question #1 Sahih al-Bukhari 5317, Book 68, Hadith 66 : What are the conditions for a woman to remarry her first husband after being divorced and marrying another man?

Rifa`a Al-Qurazi married a lady and then divorced her whereupon she married another man. She came
to the Prophet (ﷺ) and said that her new husband did not approach her, and that he was completely
impotent. The Prophet (ﷺ) said (to her), “No (you cannot remarry your first husband) till you taste the
second husband and he tastes you (i.e. till he consummates his marriage with you).