It is narrated from Sayyiduna Hudhayfah (may Allah be pleased with him) that he said to his wife: If you would like to be my wife in Paradise as well, then do not marry anyone else after me, for in Paradise a woman will belong to the last of her husbands in this world. That is why marrying the wives of the Prophet (peace and blessings be upon him) was made unlawful, because they will be his (peace and blessings be upon him) wives in Paradise as well.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13421