If a man wishes to divorce his wife he must give her a bill of divorce (get) before witnesses, as it says "And if she does not find favor in his eyes ... he shall write her a bill of divorce and put it in her hand and send her out of his house".^1,a He should not divorce her unless he has found her behavior improper, as it says "If he has found something improper about her".¹ A man should not live with his wife if he intends to divorce her, except by mutual agreement.^b

If a man divorces his wife and she becomes betrothed to another man she is forbidden to return to her first husband even if the second one divorces her or dies, as it says "And if she leaves his house and goes and becomes (wife) to another man... her first husband who sent her away cannot take her again to be his wife".^2,c A woman who is divorced or widowed should not remarry for 90 days in order to determine whether she is pregnant, so it can be decided whether the child is the first man's or the second's.^d A man should not marry a woman who is pregnant with or nursing another man's child.^e

Sources:
1. Deut. 24:1	a. 1:1-3
2. Deut. 24:2-4	b. 10:21; Issurei Biah 21:28
	c. 11:12-13
	d. 11:18
	e. 11:25