Matthew 5:32

AUV(i) 32 But I say to you, every person who divorces his wife makes her become sexually unfaithful to him [i.e., since she will probably marry someone else], unless the reason for the divorce is that she had [already] become sexually unfaithful to him. And whoever marries a woman who has been divorced commits sexual sin with her [i.e., because she is still rightfully married to her first husband].