The Qur'an cites numerous examples of unreasoning human behaviour throughout history. Without a doubt learning about these examples will help one to comprehend the costs of thoughtlessness and to avoiding its consequences.
Allah's giving Qarun, one of the people of Musa (as), great wealth is thus described in the Qur'an:
Qarun was one of the people of Musa but he lorded it over them. We gave him such treasures, that their very keys would have weighed down a band of strong men. When his people said to him, "Do not gloat. Allah does not love people who gloat. Seek rather the abode of the Hereafter with what Allah has given you, without forgetting your share in this world. and do good as Allah has been good to you. and do not seek to cause corruption in the land. Allah does not love corrupters". (Surat al-Qasas: 76-77)
As is seen in the above verses, his people warn him not to forget that it is Allah Who has given him all this wealth, to thank Allah, and use his wealth in a way that would please Allah. But, Qarun grew arrogant and insisted that this wealth had been given to him because he possessed a certain knowledge.
He said, "I have only been given these riches because of the knowledge I have". Did he not know that before him Allah had destroyed generations with far greater strength than his and far more possessions? The evil-doers shall not be questioned about their sins. (Surat al-Qasas: 78)
Qarun's fascination with wealth and thinking he possessed it because of himself was thoughtless behaviour, since the only real owner of wealth is Allah: He can give wealth to whomever He wills, whenever He wants and take it away whenever He desires. After Allah makes His decision, neither a person's knowledge, wealth, nor possessions can change this decision.
Here is where Qarun's thoughtlessness was exposed. He acted with arrogance, thinking that his treasures would be able to save him in the face of Allah's warning and punishment. Instead of thanking Allah by using this wealth in order to please Him, he tried to gain the respect of others with his possessions.
Qarun's thoughtless behaviour exposed the other thoughtless people in his tribe, who looked at Qarun in the midst of his ostentatious wealth envied him and wanted to be in his place. People with wisdom, on the other hand, condemned their behaviours by reminding them that meriting Allah's approval was much better than all the magnificence and richness of the world:
He went out among his people in his finery. Those who desired the life of the world said, "Oh! If only we had the same as Qarun has been given! What immense good fortune he possesses". But those who had been given knowledge said, "Woe to you! Allah's reward is better for those who believe and act rightly. But only the steadfast will obtain it". (Surat al-Qasas: 79-80)
Finally, because of his foolish arrogance, Allah obliterated both Qarun and his wealth. Neither his riches, nor the other things he claimed to possess could save him from this punishment. Those who had longed the day before, to be in Qarun's place as a result of being deluded by the adornment of the world, now realized how wrong they had been when they saw what happened to Qarun:
We caused the earth to swallow up both him and his house. There was no one to come to his aid, besides Allah, and he was unable to defend himself. Those who had longed to take his place the day before woke up saying, "Allah gives abundantly to any of His servants He wills and sparingly to whom He pleases. If Allah had not shown great kindness to us, we would have been swallowed up as well. Ah! Truly, the unbelievers shall never be successful". As for the abode of the Hereafter—We shall grant it to those who do not seek to exalt themselves in this world or to cause corruption in it. The successful outcome is for those who believe. (Surat al-Qasas: 81-83)
People who are mentioned as owners of the garden in the Qur'an, fell into a similar error as that of Qarun, being guilty of thoughtless behaviour. They also failed to remember that the garden they owned was a blessing given to them by Allah. This is how their situation is mentioned in the Qur'an:
We have afflicted them as We afflicted the owners of the garden when they swore that they would pluck the fruits the next morning, without saying the redeeming words, "If Allah wills". (Surat al-Qalam: 17-18)
This is the point where the owners of the garden were thoughtless, because no one can ever be definitely sure of what will happen in the future. Allah can put a person in an unexpected situation or a very different environment, whenever He wills. For this reason, the best and wisest thing to do in this situation is to be aware that one can only do something if Allah permits, and to ask Allah's permission. The Qur'an lays down how one should behave in such a situation:
Never say about anything, "I am doing that tomorrow", without adding "If Allah wills". Remember your Lord when you forget, and say, "Hopefully my Lord will guide me to something closer to the Truth". (Surat al-Kahf: 23-24)
The mistake made by the owners of the garden in this situation, was to forget that the owner and ruler of everything is Allah. When they went there early in the morning, they clearly saw that they had been greatly mistaken and now saw the seriousness of their thoughtlessness. To make them understand that the real possessor of power and wealth was Himself alone, Allah sent a plague upon their garden and dried the crops from their roots:
So a visitation from your Lord came upon it while they slept and in the morning it was like burnt land stripped bare. (Surat al-Qalam: 19-20)
The owners of the garden were talking among themselves, as they were about to go their garden in the morning, they voiced their greed in worldly goods as:
In the morning they called out to one another, "Leave early for your garden if you want to pick the fruit". So they set off, quietly saying to one another, "Do not let any poor man into it today while you are there". They left early, intent on carrying out their scheme. (Surat al-Qalam: 21-25)
So, this was another mistake they made. When they voiced their worldly greed, they forgot that Allah was a witness to it. They thought that by going to their garden early, they could avoid running into poor people. However, once Allah wills something, they don't have the power to prevent it from happening, whatever they do. As they had been extremely greedy about the crops they were going to harvest, when they saw what had happened to their garden they were baffled and thought they had come to the wrong place. But, later on they realized that the reason for this was because they had not been sufficiently grateful to Allah, and they began to condemn themselves:
But when they saw it, they said, "We must have lost our way. No, the truth is we are destitute!" The best of them said, "Did I not say to you, 'Why do you not glorify Allah?'" They said, "Glory be to our Lord! Truly we have been wrongdoers". They turned to face each other in mutual accusation. They said, "Woe to us! We were indeed transgressors. Maybe our Lord will give us something better than this in exchange. We entreat our Lord". (Surat al-Qalam: 26-32)
Prophet Nuh (as) invited his people to believe in Allah, but except for a small group of people, they didn't accept his pleas. Then Allah informed Nuh (as) that He would send down a disaster to destroy them:
It was revealed to Nuh: "None of your people are going to believe except for those who have already believed, so do not be distressed at what they do. Build the Ark under Our supervision and as We reveal, and do not plead with Me concerning the wrongdoers. They shall be drowned". (Surah Hud: 36-37)
The Prophet Nuh (as) built an ark as he was told by Allah in the above verse. Then, he brought believers and his family on to this ark at Allah's command.
When Our will was done, and water bubbled up from the earth, We said to Nuh, "Load into the Ark a pair of every species, and your family—except for those already doomed—and all who believe". But those who believed with him were only a few. He said, "Embark in it. In the name of Allah it shall set sail and cast anchor! Truly my Lord is Ever-Forgiving, and Most Merciful". (Surah Hud: 40-41)
However, Nuh (as)'s son didn't board the ark and chose to stay with the unbelievers. Nuh (as), who knew that Allah would drown them, warned his son to board the ark and not to stay with the unbelievers. However, his son insisted, saying that he would take refuge on a mountain and that the mountain would save him from this flood disaster:
It sailed with them through mountainous waves, and Nuh called out to his son, who had kept himself apart, "My son! Come on board with us. Do not stay with the unbelievers!" He said, "I will take refuge on a mountain; It will protect me from the flood". He said, "There is no protection from Allah's judgement today, except for those He has mercy on". The waves surged in between them and he was among the drowned. It was said, "Earth, swallow up your waters!" and, "Heaven, hold back your rain!" The water subsided and His will was done. The Ark came to land on al-Judi. and it was said, "Away with the wrongdoers!" (Surah Hud: 42-44)
Without a doubt, it was not possible for Nuh's (as) son to escape from the great waves and the mountain could not save him. The thoughtless error Nuh (as)'s son fell into at this point was not comprehending that no one but Allah could save him from this calamity that He had sent down. Because, as it was Allah Who created the waves, He also created the mountains and it was He Who subjected them to Him. After Allah wishes to destroy an individual or a community, there is no power or shelter that can defy Him.
In fact, Nuh (as) reminded his son of the truth by saying, "There is no protection from Allah's judgement today except for those He has mercy on" but his son did not take this important advice into consideration. Even though he was warned, he did not obey Allah's messenger and, as a result of his thoughtlessness, he received his punishment by drowning under the waves.