Is Allah not sufficient for His servant? Yet they try to scare you with others apart from Him. If Allah misguides someone, he has no guide. (Surat az-Zumar, 39:36)
Those who do not have a firm belief in Allah are afraid of many things, such as other people and natural disasters. Others are obsessed with losing their possessions or their loved ones. However, Allah addresses those who have firm belief in Him as follows:
The Lord of the heavens and Earth and everything in between them, if you are people with certainty. There is no deity but Him—He gives life and causes to die—your Lord and the Lord of your forefathers, the previous peoples. (Surat ad-Dukhan, 44:7-8)
As Allah informs us, He is the One God. Believers are well aware that nothing can harm or help them without Allah's permission. In the face of hardship, they turn to Allah out of their awareness that only He will help and answer their prayers. They do so because they know that He is the Almighty and that all other beings are powerless, unless He wills otherwise.
Thus, for believers only Allah can answer their calls for help and guidance. This means that they have no need to fear any other being or person. About this issue, the latter part of the verse above, “Is Allah not sufficient for His servant?” reads as follows:
… and if Allah guides someone, he cannot be misguided. Is Allah not Almighty, Exactor of Revenge? ... If you ask them: “Who created the heavens and Earth?” they will say: “Allah.” Say: “So what do you think? If Allah desires harm for me, can those you call upon besides Allah remove His harm? Or if He desires mercy for me, can they withhold His mercy?” Say: “Allah is enough for me. All those who truly trust put their trust in Him.” (Surat az-Zumar, 39:37-38)