Relying on Allah is one of the greatest forms of worship. Allah Says (what means): “…And upon Allah rely, if you should be believers.” (Quran 5: 23). Allah Almighty made relying upon Him a condition for faith. Allah said to His Prophet 
(what means): “…Rely upon Allah. Indeed, Allah loves those who rely [upon Him].” (Quran 3: 159)
Allah also Says (what means): “…And whoever relies upon Allah — then He is sufficient for him.” (Quran 65: 3)
Furthermore, Allah has linked this reliance to worship, as occurs in His statement (which means): “…So worship Him and rely upon Him.” (Quran 11: 123)
The meaning of reliance on Allah:
Reliance on Allah means entrusting one’s affairs to Allah and relying on Him in all matters. Entrusting one’s affairs to Allah entails not turning to something or someone else for support.
So reliance on Allah can be with regard to matters of creed, such that the servant’s heart does not turn to anyone else besides Allah. Therefore, he is always putting his reliance in Allah, entrusting all of his affairs to Him.
The pagans did not fall into polytheism and disbelief except due to the fact that they put their reliance in other than Allah, entrusted their affairs to other than Him, and believed in their hearts that someone besides Allah was able to grant their requests, alleviate their worries and repel harms from them. So they relied on statues, idols, trees, stones, graves, shrines and the deceased. They put their trust in created beings to grant them things that only Allah could do. So they began to ask them for help, offer sacrifices to them, make oaths to them, and direct various forms of worship to them.
This is since they relied on them apart from Allah, thinking that they have the power to benefit them, harm them or grant their requests. Due to this, when they put their reliance in other than Allah and directed their beliefs and worship to other than Him, they disbelieved in Him.
Relying upon Allah is from the actions of the heart – so it is an act of worship of the heart. Therefore, putting one’s trust in Allah is not to be done with one’s limbs and body parts. Rather, it is found in the heart, just like fear, awe, longing, dreading and dutifulness of Allah – all of these are acts of worship of the heart.
The position of reliance on Allah:
The position of reliance on Allah is as some of the scholars have stated: “The position of reliance upon Allah in the religion is like that of the head on a body.”
So a person who does not have reliance upon Allah does not have religion, just like a body that has no head. If the religion lacks reliance upon Allah, it lacks correctness – meaning that one will not have a correct religion.
Relying on Allah has a great standing amongst the stations of servitude to Allah. Allah distinguishes by it His believing servants from everyone else. Whoever doesn’t put his trust in Allah at all is a disbeliever. And whoever puts his trust in Allah and also on others besides Allah is a polytheist. And as for the one who puts his trust in Allah alone – he is a monotheistic believer whom Allah loves and whose actions and statements He is pleased with. This is since he has established his actions and statements upon a correct foundation.
The foundation of Shirk (polytheism) is: entrusting one’s affairs and putting one’s reliance on other than Allah. This is why Allah Says (what means): “…And upon Allah rely, if you should be believers.” [Quran 5: 23]
Allah has made reliance on Allah here a sign of one’s Faith in Him and proof of one’s monotheism.
As for the one who claims to be a believer and an adherent of monotheism, but yet then goes on to put his trust in other than Allah, such as stones, trees, statues, graves, the deceased, and so on, then this person’s claim is false. And he is not a believer because he has entrusted his affairs to someone besides Allah.
Relying upon Allah can be in religious matters as well as worldly matters. Thus you should rely on Allah in your creed and your monotheism as well as for fulfilling your worldly needs, such as seeking provision, clothing and accomplishing some set goals. Put your reliance and trust in Allah for all matters.
When it comes to fulfilling any goal, do not rely on anyone besides Allah. This is since all of the affairs are in the Hand of Allah. The keys of the Heavens and the Earth are in His Hand, so we must put our trust and reliance in Him.