From Sahih Bukhari (Hadith 5350):
Narrated Ibn `Umar:The Prophet (ﷺ) 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 (ﷺ) 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
Reference: Bukhari 5350