Believing in the divine will and decree has a great positive impact on people and on the way in which they interact with one another.
3.1. It is a way to rid oneself of shirk (associating others with Allah)
Many philosophers claim that good comes from Allah and evil is the work of lesser gods! They only said this in order to avoid attributing evil to Him Allah, may He be glorified and exalted. The Zoroastrians claimed that light is the creator of good and darkness is the creator of evil. Those of this ummah who claim that Allah does not create people’s actions or that He does not create their evil actions claim that there are two creators besides Allah. But Tawhid (affirmation of Allah’s oneness) cannot be valid unless one affirms that Allah alone is the Creator of everything in this universe and that His will is always done in His creation; whatever He wills happens and whatever He does not will does not happen.

3.2. Steadfast adherence to the straight path in times of both ease and hardship
Believing in the divine decree makes a person spend his life adhering steadfastly to the straight path; times of ease do not cause him to drift away and calamities do not make him despair, for he knows that everything that reaches him of blessings and good things is from Allah, and is not because of his smartness and good management of his affairs.

Allah, may He be glorified and exalted, says (interpretation of the meaning), "No calamity befalls the earth or your own selves but it is already written in a Book before We make it happen. Verily, that is easy for Allah. Know this so that you do not grieve for what passes you by, nor exult over what He gives you, for Allah does not love anyone who is conceited and boastful." (al-Hadid 57:22-23) "No calamity occurs except by Allah’s leave. Whoever believes in Allah, He will guide his heart aright. And Allah has knowledge of all things." (al-Taghabun 64:11)

And Allah praises His slaves, as He says (interpretation of the meaning), "Who say, when afflicted with calamity: To Allah we belong, and to Him is our return. They are the ones on whom blessings and mercy from their Lord are bestowed, and they are the ones who are guided." (al-Baqarah 2:156-157)

It was narrated that Suhayb (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said, “How wonderful is the situation of the believer, for all his affairs are good, and that is only for the believer. If something good happens to him, he gives thanks for it and that is good for him; if something bad happens to him, he bears it with patience, and that is good for him.” (Muslim)

Abu’l-‘Abbas al-Qurtubi said, “The believer here is the one who has knowledge about Allah, is content with His decrees and strives to attain what Allah has promised to the believer. That is because the believer mentioned in this hadith will be tested either with what hurts him or with what pleases him. In the former case he will show patience and seek reward, and will be content with Allah’s decree, and thus he will attain the best of this world and the hereafter and will find ease in both realms. If it is the latter case, he acknowledges the blessing and favour that Allah has bestowed upon him, and expresses gratitude and uses it to do good, and thus he will attain blessing in this world and in the hereafter.”

3.3. Motivation to do righteous deeds and strive to please Allah, may He be glorified and exalted,
Believing in the divine decree is one of the great motives that prompts one to be active and strive hard. It is one of the strongest motivations for the believer, which gives him the courage to try hard to achieve great things, with steadfastness, firm resolve and certain faith.

Belief in the divine will and decree does not mean at all that one should surrender to what Allah has decreed by giving up and not striving to change what may befall one of poverty, sickness or ignorance, and not trying to resist that. And belief in the divine decree does not mean that there is no need to strive and seek provision. The believers are enjoined to take appropriate measures, whilst also putting their trust in Allah, may He be glorified and exalted. Means and measures cannot lead to the hoped-for results except by Allah’s leave, for He created the means and measures, and He created the outcomes, and He has forbidden the Muslim to refrain from taking appropriate measures.

It was narrated from Abu Hurayrah (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) said, “The strong believer is better and more beloved to Allah than the weak believer, although both are good. Strive to do that which will benefit you and seek the help of Allah, and do not be helpless. If anything befalls you, do not say ‘If only I had done such and such, then such and such would have happened,’ rather say: ‘Allah has decreed and what He willed He did,’ for ‘if only’ opens the door to the work of the Shaytan.” (Muslim)

Ibn Taymiyah said, “Whoever thinks that putting one’s trust in Allah means that there is no need to take appropriate measures as enjoined is misguided. He is like one who thinks that he can rely on what is decreed as to who is blessed and who is doomed, without doing what Allah has enjoined.”

3.4. Facing difficulties and dangers with steadfastness
If a person believes that everything that happens to him is decreed, and he believes that provision and lifespans are in the hands of Allah, then he will have the courage to face difficulties and trials with steadfastness and firm resolve.

Allah, may He be glorified and exalted, says (interpretation of the meaning), "If anything good happens to you, it grieves them; but if some misfortune overtakes you, they say: We took our precautions beforehand, and they turn away rejoicing. Say: Nothing will ever happen to us except what Allah has decreed for us; He is our Master. And in Allah let the believers put their trust. Say: Are you waiting for anything to happen to us except one of the two good things victory or martyrdom? But we are waiting for Allah to afflict you with a punishment, either from Himself or at our hands. So wait; we too are waiting." (al-Tawbah 9:50-52)

This belief is one of the greatest factors and reasons that enabled the righteous to confront the wrongdoers and tyrants without fearing the reproach of any reproacher, because they knew that all things are in the hands of Allah and what is decreed for them would surely come to them. Thus they were not afraid to speak the word of truth for fear that their provision would cease, for provision is in the hand of Allah; whatever Allah has decreed of provision, no one can withhold it, and whatever Allah withholds from one of His slaves, no one can deliver it to him.

It was narrated that ‘Abdullah ibn ‘Abbas (may Allah be pleased with him) said, "I was riding behind the Prophet (blessings and peace of Allah be upon him) one day and he said, 'O boy, let me give you some advice: be mindful of Allah and Allah will take care of you; be mindful of Allah and you will find Him in front of you; if you ask, ask of Allah, and if you seek help, seek help from Allah. Know that if the nation were to come together to benefit you, they could not benefit you with anything but that which Allah has already decreed for you, and know if the nation were to come together to harm you, they could not harm you with anything but that which Allah has already decreed for you. The pens have been lifted and the pages have dried.'" (Ahmad. Sahih)

3.5. Believing in the divine decree makes a person realise his true status and value
Believing in the divine decree makes a person realise his true status and that he is helpless and in constant need of Allah, may He be glorified and exalted. Thus he will not become arrogant and look down on people, because he cannot know what is decreed for him or what will happen to him in the coming days.

Ibn ‘Uthaymin said, listing some of the benefits of believing in the divine decree: “It helps him to avoid self-admiration when he gets what he wants, for attaining that is a blessing from Allah because of what He had made available to him of means that led to a good outcome and success, so he gives thanks to Allah, may He be glorified and exalted, for that and does not give in to self-admiration.”

3.6. Believing in the divine decree puts an end to many of the troubles that cause great harm to communities
Believing in the divine decree puts an end to many of the ills that cause mischief in communities and create bridges between individuals. For example, the believer does not envy people for what Allah has given them of His bounty, because it is He Who granted their provision and decreed that for them. The believer knows that when he envies other people, in reality he is objecting to what Allah has decreed. The believer strives to do good and loves for people what he loves for himself. When he attains what he aspired to attain, he praises Allah and gives thanks to Him for His blessing, and when he does not attain any of that, he bears it with patience and does not panic, and he does not resent others who attained the blessings that he could not attain, because it is Allah who allocates shares of provision and gives and withholds as He wills. All of that is a test and trial from Allah, may He be glorified and exalted, to His creation.