Is it permissible, in Islamic law, to withdraw funds from one's work custody to meet personal needs, and then repay them later without anyone's knowledge?

It is forbidden for a trustee of funds to borrow from them if he is insolvent and unable to repay, or if the funds are from specific commodities (such as animals or goods). It is disliked to borrow them if they are in cash or from fungible items, and the depositor has not given him permission to do so.

If the funds are from specific commodities, it is absolutely forbidden to borrow them without the owner's permission. If they are from fungible items, it is forbidden to borrow them if the borrower is insolvent, and it is disliked if he is solvent. The dislike applies when the depositor has not given him permission to do so.

Therefore, one must avoid withdrawing funds for personal use because this is often unauthorized, especially if it will increase the borrower's inability to repay.