Ma'bad and Ubayd (the sons of Imran bin Dhuhl) said: A man was brought to Sayyiduna Ibn Mas'ud (may Allah be pleased with him), and he said: I have committed adultery. He said: "Then, if you are married, we will stone you." The people said: He only had (intercourse) with his wife's slave woman. Sayyiduna Abdullah (may Allah be pleased with him) said: "If you forced her, then free her, and give your wife a slave woman in her place." He said: By Allah, I forced her and beat her too. So he did not stone him; rather, he gave an order, and he was beaten with less than the prescribed punishment (hadd).
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9653