Torah Temimah cites R’ Akiva.
“And commits a trespass against Hashem” — because the depositor deposits without a document and without witnesses, and only the Holy One knows of them.
Diyuk of “baHashem” — deposit fraud is a sin against God because human proof is often absent.
The verse frames deposit fraud as a sin against God because human proof is often absent. The depositor relies on the recipient’s honesty and on Heaven’s knowledge; a false denial is therefore a ma’al against Hashem as well as against one’s fellow.