Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) says: An impotent man is given a respite of one year. If he has relations with the woman, well and good; otherwise the husband and wife are separated, and the woman receives the dower.
Al-Tabarani recorded it, and its narrators are the narrators of the Sahih except Husayn bin Qabisah, who is thiqah (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب النكاح / 7609