من لا يحضره الفقيه, volume 4, page 24

Hadith.4991 - Aṣim ibn Humayd narrated from Muhammad ibn Qays from Abu Jafar Imam Muhammad ibn Ali Al-Baqir (as) who said: "The Commander of the Faithful (as) said: "A man or a woman shall not be flogged until four witnesses testify explicitly to the act of penetration and withdrawal." Imam (as) also said: "I will not be the first among the four witnesses because I fear that one of them might retract their testimony, and I would then be subjected to flogging."

Translation: Bab Ul Qaim Publications — attributed by Thaqalayn·The Arabic above is the original.

Hadith.4992 - Faḍalah narrated from Dawud ibn Abi Yazid who said: I heard Abu Abdullah (as) say: "The companions of the Messenger of Allah (swt) (peace be upon him and his family) said to Saʿd ibn Ubadah, 'What would you do if you found a man with your wife?' He (Sa'd) replied: 'I would strike him with the sword.' Then the Messenger of Allah (swt) (peace be upon him and his family) came out and said: 'What is this, O' Saʿd?' Saʿd said: 'They asked me what I would do if I found a man with my wife, and I said I would strike him with the sword.' The Prophet (peace be upon him and his family) said: 'O' Saʿd, but what about the requirement of four witnesses?' Saʿd replied: 'O' Messenger of Allah (swt), even after seeing it with my own eyes and knowing, as Allah (swt) knows, that it has happened?' The Prophet (peace be upon him and his family) said: 'Yes, by Allah (swt), even after you see it with your own eyes and Allah (swt) knows it has happened, because Allah (swt), the Glorious and Exalted, has set limits for everything, and for whoever transgresses these limits, Allah (swt) has also prescribed a punishment.'"

Translation: Bab Ul Qaim Publications — attributed by Thaqalayn·The Arabic above is the original.