A freed slave of Amr bin al-As (may Allah be pleased with him) narrated that Amr sent him to Sayyiduna Ali (may Allah be pleased with him) to seek permission to enter upon Sayyidah Asma' bint Umays (may Allah be pleased with her). He granted him permission. When he had finished his business, the freed slave asked Amr about that, and he said: The Prophet (peace and blessings be upon him) "forbade us from entering upon women without the permission of their husbands."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13520