Salamah bin Abdullah bin Salamah bin Abi Salamah narrates from his father, and he from his grandfather (may Allah be pleased with him), that the Prophet (peace and blessings be upon him) proposed marriage to Umm Salamah (may Allah be pleased with her). He (peace and blessings be upon him) said: "Tell your son to marry you (to me)," or he said: "Her son married her (to him)," and he had not yet even reached puberty.
The Shaykh said: In matters of marriage, the Prophet (peace and blessings be upon him) had (privileges) that no one else had.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13754