We are truly sorry to hear about the suffering that is being endured. It is heartbreaking to be subject to ailments and pain. In such difficult times let us seek God's will together in Jesus' name.
First, we want to acknowledge the elephant in the room. It is important that we address the request to end his and our suffering by passing away peacefully. As difficult as suffering is we must remember and be encouraged in the account of Paul. He suffered greatly for the cause of Christ. While it is not specifically stated that he suffered ailments or pain, he did suffer persecution and imprisonment. When he was suffering he prayed to the Lord in 2 Corinthians 12:8-9 WEB, "Concerning this thing, I begged the Lord three times that it might depart from me. He has said to me, 'My grace is sufficient for you, for my power is made perfect in weakness.' Most gladly therefore I will rather glory in my weaknesses, that the power of Christ may rest on me." We do not find Paul asking to end his suffering by passing away peacefully.
Furthermore, we must keep in mind God's warning in 1 Corinthians 3:16-17 WEB, "Do you not know that you are a temple of God, and that God's Spirit lives in you? If anyone destroys the temple of God, God will destroy him; for God's temple is holy, which you are."
We do not know if the suffering is a trial that God has allowed as in the case of Job. When Job had lost everything, his wife told him to curse God and die in Job 2:9. Job did not listen to his wife. Later Job said to his so-called friends in Job 13:15 WEB, "Though he kill me, yet I will trust him, ...".
Lastly, regarding the suffering and passing away we find in Romans 14:7-8, "For none of us lives to himself, and none dies to himself. For if we live, we live to the Lord. Or if we die, we die to the Lord. If therefore we live or die, we are the Lord's." And in Philippians 1:20 WEB, "according to my earnest expectation and hope, that I will be ashamed in nothing, but that with all boldness, as always, even now Christ will be magnified in my body, whether by life or by death." The gospel is preached even in his suffering.
If this request was prayed without lifting up the name of Jesus Christ, then we strongly urge to reconsider who they are praying to. It is only by the name of Jesus Christ that we have access to God. In John 14:6 WEB Jesus says, "I am the way, the truth, and the life. No one comes to the Father, except through me." The writer of Acts records in Acts 4:12 WEB, "There is salvation in none other, for neither is there any other name under heaven, that is given among men, by which we must be saved!"
Let us pray together.
Heavenly Father,
We come before You in the name of Jesus Christ lifting up this person who is suffering. We ask You to be the Great Physician that You are and heal him. We ask You to help them to endure and persevere through this trial. We ask You to continue to make Yourself known to them and to demonstrate Your character and goodness through this trial. Help them to honor and glorify You in their life and even in their death if that is Your will. Help them to overcome this trial and to grow closer to You through it.
In the name of Jesus Christ we pray. Amen.