Sahih Bukhari Volume 7, Book 68, Hadith 5352

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرٍو، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ لِلْمُتَلاَعِنَيْنِ ‏"‏ حِسَابُكُمَا عَلَى اللَّهِ، أَحَدُكُمَا كَاذِبٌ، لاَ سَبِيلَ لَكَ عَلَيْهَا ‏"‏‏.‏ قَالَ يَا رَسُولَ اللَّهِ مَالِي‏.‏ قَالَ ‏"‏ لاَ مَالَ لَكَ، إِنْ كُنْتَ صَدَقْتَ عَلَيْهَا، فَهْوَ بِمَا اسْتَحْلَلْتَ مِنْ فَرْجِهَا، وَإِنْ كُنْتَ كَذَبْتَ عَلَيْهَا، فَذَاكَ أَبْعَدُ وَأَبْعَدُ لَكَ مِنْهَا ‏"‏‏

Narrated By Ibn 'Umar : The Prophet said to those who were involved in a case of Lian, "Your accounts are with Allah. One of you two is a liar. You (husband) have right on her (wife)." The husband said, "My money, O Allah's Apostle!" The Prophet said, "You are not entitled to take back any money. If you have told the truth, the Mahr that you paid, was for having sexual relations with her lawfully; and if you are a liar, then you are less entitled to get it back."