Abdullah bin Ubayd bin Umayr (may Allah have mercy on him) said: Abd al-Rahman bin Awf (may Allah be pleased with him) sold a slave-girl. He used to have intercourse with her, (and sold her) before istibra' (establishing that her womb was clear), and the pregnancy became apparent while she was with the buyer, so the dispute came to Sayyiduna Umar (may Allah be pleased with him). Sayyiduna Umar (may Allah be pleased with him) called a physiognomist, who looked and attached (the child) to him. In another place (it is reported) that Sayyiduna Umar (may Allah be pleased with him) asked: Did you have intercourse with her? He said: Yes. Sayyiduna Umar (may Allah be pleased with him) said: You sold her before istibra'? He said: Yes. He said: That was not fitting of you. Then Sayyiduna Umar (may Allah be pleased with him) called the physiognomist.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الدعوى والبينات / 21264