Abu Hurairah (may Allah be pleased with him) reports that the Prophet Muhammad (peace and blessings be upon him) said: "Return the trust to the one who entrusted you, and do not betray the one who betrays you." __QUR_N__ __XREF_N__ __REF_N__

Imam Tirmidhi says:
1- This hadith is Hasan Gharib.
2- Some people of knowledge have followed this hadith. They say that when a person has something belonging to another in his charge, and he takes it away, then if something belonging to that person comes into his possession, it is not permissible for him to withhold from it as much as was taken from him.
3- Some of the Tabi'in among the people of knowledge have permitted this, and this is also the opinion of Sufyan al-Thawri. He says: If someone owes him dirhams, and dinars (as a trust) come into his possession, it is not permissible for him to withhold the dinars in exchange for his dirhams. However, if dirhams come into his possession, then it is permissible for him to withhold from the dirhams as much as is owed to him.