For every business partnership or transaction, we must sign a contract or bring witnesses to ensure that one side does not renege. Yet when someone deposits something of value with a friend, he often relies on the friend’s integrity without requiring a signed contract. One who falsely denies a deposit entrusted to him is referred to in Torah as one who “betrayed the L-rd.” Other than the two parties to the agreement, G-d is the only One Who knows the truth. Thus, denying a pledge is betraying the L-rd. As Rashi says in his commentary, “He denies the third in their midst.”
The expression “the third in their midst” emphasizes that G-d is not only a witness but a participant in the matter. The depositor and the trustee are the two parties, and the third is G-d, the true owner of the deposit, because the world and all its glory belong to Him. When we falsely take what is not ours, we betray not only our friend but G-d Himself.
Despite the severity of this act, it is still possible to do teshuvah. The Torah stipulates what he must do to atone, and then G-d will forgive him. The power of teshuvah is so great that even for such a serious sin, teshuvah is accepted immediately.
Of course, we cannot atone for any sin until we have personally asked forgiveness from the person we wronged. Only then will G-d grant His forgiveness. But the minute we decide to correct our misdeeds, G-d is ready to accept our apology. Thus, Maimonides states, “In the end everyone will do teshuvah and will immediately be redeemed.”