This is one of my favorite prayers from rejoice ministries:
Stand in the gap for your marriage. Do not give up, get on your knees daily and annoying his pillow.
LORD, we pray that no weapon formed against this family will prevail. Satan, you were defeated at the cross when our Lord Jesus Christ was crucified. He arose showing you His mighty resurrection power. Get away from this family and all families around the world who are speaking separation and divorce. God hates divorce, instead he will be the Repairer of Broken Walls, a Repairer of the Breech and will rebuild their homes on the solid rock of Jesus Christ.
LORD, we pray that all the spouses who are planning on leaving and the ones who are gone, will flee the evil desires of youth, and instead pursue righteousness, faith, love and peace, along with those who call on the Lord out of a pure heart. (2 Timothy 2:22) We pray that they will come to their senses and escape from the trap of the devil, who has taken them captive to do his will. (2 Timothy 2:26) We know that Your sheep hear Your voice, so speak loudly to Your children today and we pray that they will be obedient to Your voice, Your will, and Your way. We pray this in the mighty name of our Lord Jesus Christ. Amen.