Follow what has been revealed to you from your Lord - there is no god but Him - and turn away from the idolaters. (Surat al-An'am: 106)
Allah chose our Prophet (saas) and revealed to him the Qur'an, which will apply until the Day of Judgment. The Qur'an also informs us that Prophet Muhammad (saas) is the last Prophet. Our Prophet (saas) adhered to the Qur'an and advised people to read it and respect only its judgments. The related verses are as follows:
Say: "I do not say to you that I possess the treasuries of Allah, nor do I know the Unseen, nor do I say to you that I am an angel. I only follow what has been revealed to me." Say: "Are the blind the same as those who can see? So will you not reflect?" (Surat al-An'am: 50)
Follow what has been revealed to you and be steadfast until Allah's judgement comes. He is the Best of Judges. (Surah Yunus: 109)
Our Prophet (saas) also recommended to his companions that they read the Qur'an and observe its commands:
Why do some people impose conditions that are not present in Allah's Book (Laws)? Whoever imposes a condition that is not in Allah's Laws, then that condition is invalid even if he imposes one hundred conditions, for Allah's conditions are more binding and reliable. (Bukhari)
Allah's Book is Allah's rope; he who follows it has guidance, and he who abandons it is in error. (Muslim)
He who spoke according to the Qur'an spoke the truth, and he who acts in accordance with its directions entitles himself to reward. Again, he who judges according to the Qur'an is just and fair. Then, as for him who invites people to the Qur'an is indeed guided on the Right Path. (Tirmidhi)
While enjoining good or forbidding evil, our Prophet (saas) adhered only to the Qur'an as a guide. All of his words stemmed from it: "I follow only what has been revealed to me from my Lord. This is clear insight from your Lord, and a guidance and a mercy, for people who believe" (Surat al-A'raf: 203). For instance, his people asked him for a fatwa (legal opinion concerning Islamic law) about women. Allah told His Messenger (saas) to say: "Allah gives you a fatwa about them" (Surat an-Nisa': 127). Similarly, when people asked for a fatwa about inheritance, Allah ordered him to say: "Allah gives you a fatwa about people who die without direct heirs" and "Allah makes things clear to you so you will not go astray. Allah has knowledge of all things." (Surat an-Nisa': 176)
In another verse, Allah reveals our Prophet (saas) to reply as follows to those who say: "Bring a Qur'an other than this or change it."
Say: "It is not for me to change it of my own accord. I follow nothing except what is revealed to me. I fear, were I to disobey my Lord, the punishment of a Dreadful Day." (Surah Yunus: 15)
Consequently, the Sunna of our Prophet (saas) is to apply the Qur'an to daily life. For this reason, Allah informs us that obeying him is a basic tenet of faith. In one verse, Allah states that such obedience is actually obedience to Him (Surat an-Nisa': 80). Anyone who complies with his words and follows his Sunna also observes the Qur'anic judgments, for every attitude, decision, and word of our Prophet (saas) stems from the Qur'an. In the following prophetic tradition, our Prophet (saas) said:
He who obeys me has obeyed Allah, and he who disobeys me has disobeyed Allah; he who obeys the Amir (the Ruler I appoint) has obeyed me, and he who disobeys the Amir has disobeyed me. (Bukhari)
As the Qur'an states, our Prophet (saas) was a person of moral excellence who was distressed by the believers' suffering. He was deeply concerned about the believers, and was gentle and merciful toward them (Surat at-Tawba: 128); a noble person who enjoined good and forbade wrong, and relieved the believers of their heavy loads and the chains that were around them (Surat al-A'raf: 157); and was a blessing to people, purified them, and taught them the Book and Wisdom (Surah Al 'Imran: 164).
To be a true Muslim with whom Allah is pleased, a person must obey the Qur'an's commands, embrace the Sunna of our Prophet (saas), and meticulously practice whatever they tell us to do. Since the Qur'an gives a detailed account of our Prophet's life, Muslims are obliged to examine his life, follow in his footsteps, and seek to display his moral excellence. In the Qur'an, Allah explains that the Prophet (saas) sets the best example for believers:
You have an excellent model in the Messenger of Allah, for all who put their hope in Allah and the Last Day and remember Allah much. (Surat al-Ahzab: 21)