Tawakkul (Arabic: توكل) means to depend sincerely in one’s heart upon Allaah Almighty, for bringing blessings and warding off harms, for this world and the Hereafter. If people were to sincerely trust and depend upon Allaah to bring them that which benefits them and to keep away that which harms them, and if they take reasonable, practical steps themselves, Allaah will send their provision to them by the simplest of means. Just as Allaah Almighty gives the bird provision when it simply leaves in the morning, seeking its sustenance, and returns at the end of the day. Yes, it does go out to search, but it is an easy effort. Tawakkul in reality does not deny actually working and striving for provision, for Allaah Almighty has decreed that we should work and it is from His ways that he gives people when they strive. In fact, Allaah Almighty ordered us to both depend upon Him and to work, to take the necessary steps needed to achieve our goals, and so the act of striving for our sustenance is an act of physical worship while trusting and depending upon Allaah is faith in Him.
"And in Allaah let believers put their Trust"
He made Tawakkul like Taqwa which is to establish the means that have been ordered, while depending upon Allaah. Dependence without working and striving is mere impotence, even though, when one does this, he may appear to depend on Allaah to a certain degree. No one, then, should transform his trust into mere impotence and weakness. One should rather deem his trust in Allaah to be like working and striving: it is one of the necessary steps one must take to achieve his goal.
"Were you to depend upon Allaah with true dependence, He would have provided for you like He provides for the bird; early in the morning he leaves hungry, but returns at the end of the day with a full stomach."
-At-Tirmidhi, Ibn Majah, Ahmad etc
Reliance on Allah does NOT mean not working and striving for sustenance in this life. Al-Bahaiqiy (one of the major collectors of hadith) said:
"There is no support in this hadith for resigning from working to earn. On the contrary, it in fact supports working and seeking earnings. This is because the bird when it flies out in the morning does so in pursuit of its sustenance. And so the meaning – and Allah knows best – is: if they were to rely on Allah while setting out and while returning and when acting/interacting and believed during all of that that all good id in the hands of Allah and comes only from Him, they would never set out except in a state of health and success like the birds who set out hungry and return full. If, however, they rely on their own strengths and abilities and then engage in deception, lying and insincerity, this is opposite to reliance on Allah."