He Took Money From Someone Without His Permission, But He Intended To Return It
Question :
When I used to work as a collector, I once used some money that I was responsible for, but I intended it to be an advance, which I would repay as soon as I got my salary. Before I could pay the amount back, however, my boss found out what I had done, and he demanded that I return the amount immediately, which I did without arguing. Now my conscience bothers me for what I did; what should I do to regain a clear conscience?
Answer:
By taking someone else's money that was in your hand, A you broke the trust that you had, regardless of whether your intention was to return it later. You took money from its owner who could have invested it to make profit. Moreover, you more or less disgraced yourself and blemished your honor. At least you returned the money when asked, and at least you feel remorse for what you did. But you must do more: You must resolve not to return to that sin and you must ask forgiveness from the owner of that money, so that your repentance may be more likely to be accepted, and increase in good deeds according to the Hadith:
"Follow up a sin with a good deed, and the latter will have erased the former."
Have hope that Allah Almighty will forgive you and protect you from evil deeds.
Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 7 Pages 266-267