Indeed, Tawkkul is from the greatest forms of worship. Allaah (subhaanahu wata 'a'la) said:
'... and in Allaah put your trust if you are believers indeed.' [Al-Maa'idah, 23]
So (here), He made a condition of faith: Tawakkul in Allaah (subhaanahu wata 'a'la). And He said to His Prophet (peace and blessings be upon him):
'Then when you have taken a decision, put your trust in Allaah.' [Al-Imraan, 159]
So (here), He commanded His Prophet (peace and blessings be upon him) to place his Tawakkul in Allaah (subhaanahu wata 'a'la). And He said:
'O Prophet (Muhammad)! Allaah is Sufficient for you and for the believers who follow you.' [Al-Anfaal, 64]
And He said:
'And whoever has Taqwaa* of Allaah, He will make a way for him to get out (from every difficulty). And He will provide him from (sources) he could never imagine. And whosoever puts his trust in Allaah, then He will suffice him. Verily, Allaah will accomplish his purpose. Indeed Allaah has set a measure for all things.' [At-Talaq 2-3]
*At-Taqwaa: that you make between yourself and the anger of Allaah and His punishment a shield which you protect yourself with, and that is by being obedient to Allaah and His Messenger (sallallaahu alayhi wasalam).
So (here), He coupled Tawakkul with Taqwaa. And He, the Most High, said:
'...and whosoever has Taqwaa of Allaah, He will make his matter easy for him. That is the Command of Allaah, which He has sent down to you; and whosoever has Taqwaa of Allaah and keeps his duty to Him, He will expiate from him sins, and will englarfe his reward.' [At-Talaaq, 4-5]
'...so worship Him and put your trust in Him...' [Hood,123]
And Allaah commanded Tawakkul and praised its people, and informed that He loves the people of Tawakkul in numerous Aayaat which (also) point to the importance of Tawakkul in Allaah (subhaanahu wata 'a'la).
Tawakkul in Allaah is from the actions of the heart, hence it is worship of the heart, so Tawakkul is, as some of the people of knowledge stated: 'Tawakkul from the Deen* is like the position of the head from the body.'
*What is intended by it is: submission and obedience. The Deen of Islam is the religion of this Messenger (Muhammad) sallallaahu alayhi wasalam.
So the one who does not have Tawakkul then he does not have Deen, just like the body which does not have a head to it; and it is understood that when the body loses the head, it loses life, and likewise when the Deen loses Tawakkul, it loses soundness and cannot be a correct Deen.
Tawakkul in Allaah has a tremendous place in the stations of servitude to Allaah (Az wa Jal); Allaah distinguishes His believeing slaves from other than them by it. Therefore whoever does not place Tawakkul in Allaah in essence, then indeed he is a disbeliever, and whoever places Tawakkul in Allaah and in other than Him, then he is a polytheist; and whoever places Tawakkul in Allaah alone, then indeed he is a monotheist believer whom Allaah loves and is pleased with in regards to his actions and statements, because he based them on a sound foundation.