Musannaf Ibn Abi Shaybah 18063 — A man who accepts Islam while married

Awf (may Allah have mercy on him) reported that a man of the tribe of Banu Taym Allah named Hammam bin Umayr had two full sisters (as wives or slave-women) in the days of ignorance (Jahiliyyah), and he did not separate from either of them. During the caliphate of Sayyiduna Umar (may Allah be pleased with him), his case was brought before Sayyiduna Umar (may Allah be pleased with him), who sent him word: "Choose one of the two. By Allah, if you go near the other, I will strike your head."