Allah Almighty says: "And when you divorce women and they reach the end of their waiting period, do not prevent them from marrying their (former) husbands." [Surah al-Baqarah: 232]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / Q13594
Al-Hasan (may Allah have mercy on him) said concerning the saying of Allah Almighty, "Do not prevent them from marrying their husbands" [Surah al-Baqarah: 232]: Ma'qil bin Yasar (may Allah be pleased with him) narrated to me that this verse was revealed concerning him. (He said:) I married my sister to a man. He divorced her, until her waiting period ended. Then he came and proposed marriage to her again. I said to him: I married her to you, provided you with a bed and honoured you, and you divorced her; then you come proposing to her. By Allah! I will never marry her to you. He was a man in whom there was no harm, and the woman wanted to return to her husband, so Allah Almighty revealed this verse: "And when you divorce women and they reach the end of their waiting period, do not prevent them" [Surah al-Baqarah: 232]. So I said: O Prophet of Allah (peace and blessings be upon him)! Now I will marry her (to him), and I married her (to him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13594
The sister of Sayyiduna Ma'qil bin Yasar (may Allah be pleased with him) was married to a man. He divorced her and then left her alone; when her waiting period had passed, he came near and proposed marriage to her. Sayyiduna Ma'qil (may Allah be pleased with him) felt indignant at this and said: First he separated from her although he could have taken her back, and now he comes again with a proposal! So he came between the two of them. Then Allah Almighty revealed this verse: "And when you divorce women and they reach the end of their waiting period, do not prevent them from marrying their husbands" [Surah al-Baqarah: 232]. The Messenger of Allah (peace and blessings be upon him) called him and recited this verse to him, so he abandoned his indignation and had their marriage contracted. Al-Kalbi claimed that his sister's name was Jamilah bint Yasar.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13595