Qatadah (may Allah have mercy on him) said concerning the verse "And when you said to the one on whom Allah had bestowed favour" [al-Ahzab: 37], meaning with Islam, "and on whom you had bestowed favour", meaning by freeing him, "Keep your wife to yourself" [al-Ahzab: 37] - and he is Zayd bin Harithah (may Allah be pleased with him).
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20486