This is an action of the heart. It means to put one’s trust in Allah, to cut off hope of any good from any created object, and to hope the best and reply completely on Allah.
To rely on physical and tangible means is a type of minor shirk, and to invent means and rely upon them is major shirk.
An example of minor shirk in this regards is to have your tawakkul in medicine to cure you. It is a tangible means, but to put one’s reliance in it is a form of minor shirk. The proper belief is to have tawakkul in Allah, to know that He has blessed us by providing us a means of a cure by the medicine. We take the medicine as the action (like tying your camel), and put our trust and reliance in Allah to heal us.
Tawakkul is a part of emaan.
“So put your trust in Allah if you are indeed believers.” (Al-Maa’idah, 5:23)
“Moosaa said, ‘O my people, if you have really believed in Allah, then put your trust in Him, if you are really submitters (Muslims).” (Younus, 10:84)
“And from You alone do we seek help.” (Al-Faatihah, 1:4)
True tawakkul necessitates actions.
“Oh, you who believe! Take your precaution, then go forth in detachments or go forth in a body.” (An-Nisaa’, 4:71)
“Take medicine, oh servants of Allah.” (Ibn Maajah)
You do what you are able, and your heart is attached to Allah.
The Prophet (saw) said to the Bedouin who had left his camel untied putting his trust in Allah, “Tie your camel, and put your trust in Allah.” (Saheeh ul-Jaami’ 1068)
“And furnish yourselves with necessary provisions for your journey and surely, the best provision is righteousness.” (Al-Baqarah, 2:197)
“If you put your tawakkul in Allah the way He deserves, He would provide for you the way he provides for the birds. They leave in the morning with an empty stomach and return at night with a full one.” (Tirmidhi)
This shows you have to work for your rizq.