Hayyan bin Ubaydullah said: Abu Mijlaz (may Allah have mercy on him) was asked about exchange (sarf) of money while I was present, and Abu Mijlaz Lahiq bin Humayd (may Allah have mercy on him) said: For a period of his life Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) used to say that when it is in cash there is no harm, and he used to say that usury is only in credit transactions, until he met Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him), who mentioned the hadith in a similar way: that the Prophet (peace and blessings be upon him) said: "Like must be for like, equally; whoever gives more, that is usury; and everything that is weighed or measured is likewise." Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: "O Abu Sa'id! 'Jazak Allahu khayran' (may Allah reward you with good) — may He grant you Paradise on my behalf. You have reminded me of something I had forgotten. 'Astaghfirullaha wa atubu ilayh' (I seek Allah's forgiveness and repent to Him)." And after that he used to forbid it most strictly.
Abu Ahmad (Ibn Adi) said: Only Hayyan narrates this hadith from Abu Mijlaz. Hayyan has been criticised (by the hadith critics).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10520