Tawakkul Reliance upon Allaah alone in Musnad Imam Ahmad,At-Tirmidhi,Ibn Majah

Narrated `Umar Ibn Al-Khattab that he heard the Messenger of Allaah  saying: “If you would trust in Allaah as He truly should be trusted in, He would surely provide for you as He provides for the birds. They set out in the morning with empty stomachs and return in the evening with full stomachs.”
[Musnad Imam Ahmad, Ibn Majah 4164, Tirmidhi 2344. Authenticated by Shaikh Al-Albaani, As-Saheehah 310.]

Anas bin Malik, said: "A man said: ‘O Messenger of Allaah, should I tie it (the camel) and make tawakkul,or let it go free and make tawakkul?' He  said: "Tie it and make tawakkul.'" [At-Tirmidhi]
And He will provide him from (sources) he never could imagine. And whosoever puts his trust in Allâh, then He will suffice him. Verily, Allâh will accomplish his purpose. Indeed Allâh has set a measure for all things
[Surah Al-Talq, Verse 2-3] 

Would that they were contented with what Allâh and His Messenger (SAW) gave them and had said: "Allâh is  Sufficient for us. Allâh will give us of His Bounty, and so will His Messenger (from alms, etc.). We implore Allâh (to enrich us)."
 [Surah Al-Tawba, Verse 59]