Jami` at-Tirmidhi Book 43, Hadith 50
that the Prophet (ﷺ) said: "I have not left among the people after me, a Fitnah more harmful upon men than women."
from the freed slave of 'Amr bin Al-'As that 'Amr bin Al-'As sent him to 'Ali seeking his permission to enter upon Asma bint Umais, so he permitted him. When he was finished from what he needed, the freed slave of 'Amr bin Al-'As asked about that, so he said: "Indeed the Prophet (ﷺ) prohibited us - or - prohibited that we enter upon women, without the permission of their husbands."
Another chain with a similar narration