Sayyiduna Salamah bin Sakhr (may Allah be pleased with him) narrates: In the time of the Messenger of Allah (peace and blessings be upon him), I pronounced zihar on my wife, then I had intercourse with her before offering the expiation. So I asked the Prophet (peace and blessings be upon him), and he gave me the ruling of expiation.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6305