A man came to the Prophet, and he had uttered Zihar upon his wife then he had intercourse with her. So he said: 'O Messenger of Allah! I uttered Zihar against my wife, then I had intercourse with her before atoning.' He (pbuh) said: "What caused you to do that, may Allah have mercy upon you?' He said: 'I saw her anklets in the moonlight.' He said: 'Then do not go near her until you have done what Allah ordered (for it).'"
Jami` at-Tirmidhi Book 13, Hadith 26