Bismillah
The man of simple intention works in an atmosphere of prayer: that is to say he is recollected. His spiritual reserves are not all poured out into his work, but stored where they belong, in the depths of his being, with his God. He is detached from his work and from its results. Only a man who works purely for God can at the same time do a very good job and leave the results of the job to God alone.
Ibn Katheer (may Allah have mercy on him) said:
“and I entrust my affair to Allah” means: and I rely on Allah and seek His help.
End quote from Tafseer Ibn Katheer (7/146).
Secondly:
Entrusting one’s affairs to Allah, may He be exalted, and relying on Him is something that is required in all one’s affairs, both religious and worldly. This is enjoined in many texts, such as the following:
“And upon Allah rely, if you should be believers”
[al-Maa’idah 5:23]
“…and rely upon Allah. And sufficient is Allah as Disposer of affairs”
[an-Nisa’ 4:81]
حَسْبِيَ اللهُ لا إِلَهَ إِلاَّ هُوَ عَلَيْهِ تَوَكَّلْتُ وَهُوَ رَبُّ العَرْشِ العَظِيْمِ.
‘Allah is Sufficient for me, none has the right to be worshipped except Him, upon Him I rely and He is Lord of the exalted throne.’
Aameen Ya Rabbal Alameen