We are truly sorry to hear about the trial your family is enduring. Cancer is a devastating disease, and watching a loved one suffer can be heart-wrenching. We will stand with you in prayer, seeking God's comfort and strength for your husband and his mother, and for you to support your husband in a godly wife role. He needs you and to know you are there for him.
Firstly, let's pray for your husband's mother. She needs to accept Jesus as her Lord and Savior if she does not know him. It is important she knows she can be saved. It is only by the name of Jesus that we are saved and come to the Father.
There is therefore no condemnation to those who are in Christ Jesus, who don’t walk according to the flesh, but according to the Spirit. For the law of the Spirit of life in Christ Jesus made me free from the law of sin and of death.
Romans 8:1-2 (WEB)
You need to be in prayer for her salvation. She needs to confess that Jesus Christ is Lord and believe that God raised him from the dead to be saved.
because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved.
Romans 10:9 (WEB)
In addition, pray for God's mercy and comfort upon her, asking that His will be done in her life and in her death. Trust that God is faithful, and He will be with her through this difficult time. He will not abandon her in this time of need.
Though I walk in the middle of the shadow of death, I will fear no evils; for you are with me. Your rod and your staff, they comfort me.
Psalm 23:4 (WEB)
For your husband, pray that God would comfort his broken heart and provide him with a supernatural peace that surpasses all understanding. Pray that he would draw close to God during this time and find solace in His presence.
Don’t be anxious for anything; but in everything by prayer and pleading with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all understanding, will guard your hearts and your thoughts in Christ Jesus.
Philippians 4:6-7 (WEB)
He is blessed with a believing wife. Encourage him to support and love his wife (you) as the church is to love Christ.
Also, pray that your husband would forgive any past hurts or misunderstandings between you and his mother, and that their relationship would be restored and healed before her passing. It's important to remember that forgiveness is a crucial part of our walk with Christ, and it's essential for your husband to release any bitterness or resentment he may be harboring.
For if you forgive men their trespasses, your heavenly Father will also forgive you. But if you don’t forgive men their trespasses, neither will your Father forgive your trespasses.
Matthew 6:14-15 (WEB)
As for your role in this situation, continue to be patient, loving, and supportive, even when your husband lashes out in pain. Remember that his anger is likely a result of his grief and not a reflection of his love for you. Keep praying quietly and fervently for him. It is challenging for a man to be a spiritual leader in a time of crippling grief so you need to be his strength in a godly wife role. Be the support for him in his time of need. Be there for him. God will give you the strength to be the wife he needs. Pray and ask God for His wisdom in handling this delicate time.
An intelligent woman does good to herself; for she is industrious, diligent, and faithful to her husband and family. But a foolish, wicked, and selfish woman destroys even the good which she has, and brings sorrow and disgrace to her husband and family. She doesn't know that the souls of her household are in her hand, and she will be held responsible for the way she leads her family.
Proverbs 14:1 (WEB Paraphrased)
Finally, pray that God would strengthen your marriage through this trial and draw you both closer to Him and each other.
Let's end with this prayer.
Heavenly Father,
We come before You today, lifting up this family in their time of need. Lord, we ask for Your healing touch upon the husband's mother. Comfort her and give the family wisdom to deal with her diagnosis. Lord, we pray for her salvation if she does not know Jesus.
Father, we also pray for Your comfort and peace to envelop the husband as he struggles with his mother's illness. Help him to cast all his anxieties on You, knowing that You care for him. Lord, heal his broken heart and provide him with Your supernatural strength during this time. Help him to forgive any past hurts and to draw close to You.
Lord, we also lift up the wife, asking that You grant her patience, wisdom, and unfailing love as she supports her husband. Help her to be a source of comfort and strength for him, and draw them closer together as a couple. Help them to remember that forgiveness is a crucial part of their walk with Christ, and it's essential for their relationship to release any bitterness or resentment they may be harboring.
In Jesus' name, we pray for strength, mercy, and grace to endure this trial and for God to be glorified through it all.
Amen.
Prayer Focus: God, Thank You. Thank You for loving me. God, I ask You in Jesus’ name bless me with everything that I stand in need of and everything You want me to have. Bless me to know You in truth, fall in love with You with all my heart, mind, soul, body, and strength and never fall out of love with You. Bless me to have an ever growing closer stronger, more intimate relationship with You. Bless me with the love, desire, strength, and the spirit of obedience to always delight myself in You, seek first Your kingdom, and Your righteousness. Help and strengthen me God to always respect and obey You. Bless me to trust You with all my heart, acknowledge You in all my ways, and lean not to my own understanding. 
