We understand your heartache, and we are here to lift your situation up to the Lord with you. Firstly, let's pray:
"Dear Heavenly Father, we come before You in Jesus' name to plead for this marriage. We ask that You soften [husband's] heart and draw him back to his wife. Break the bonds of any adulterous relationship, Lord, and bring conviction upon the other woman to leave this family alone. We pray for a spirit of unity and love to be restored in their marriage. In Jesus' name, we pray. Amen."
We want to encourage you with God's Word. In Malachi 2:16, it is written, "For Yahweh, the God of Israel, says that he hates divorce; for it covers one's garment with violence! Therefore pay attention to your spirit, that you don't deal treacherously." God hates divorce, and He wants marriages to work. Keep praying and believing, for with God, all things are possible (Matthew 19:26).
However, we must also address the seriousness of adultery. It is a sin against God and your spouse (Exodus 20:14). It is crucial that your husband repents and turns away from this sin. As for you, God asks you to be patient and forgiving, just as He is with us (Ephesians 4:32).
Lastly, ensure that you are both seeking God individually and together. The strength of your marriage comes from your unity in Christ. Jesus said, "If two of you will agree on earth concerning anything that they will ask, it will be done for them by my Father who is in heaven. For where two or three are gathered together in my name, there I am in the middle of them." (Matthew 18:19-20, WEB). Hold onto this promise, and keep praying together.
Remember, it is only in the name of Jesus that we have access to God. So, continue to pray in Jesus' name, and trust that He is working in your situation.