We are truly sorry to hear about your grandpa Juan's condition, and we appreciate your heartfelt concern for his spiritual well-being. It is commendable that you are interceding for him, as this aligns with the biblical principle of praying for one another, even for those who are not yet saved.
Let us remember that it is only by Jesus Christ the Lord that we are saved. If we are not with Him, we do not have access to God the Father and this is the only way to salvation. Jesus Christ died for us, in our place, for our sins as God's plan.
Ye call upon the Father, who without respect of persons judgeth according to every man's work: pass the time of your sojourning here in fear: Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers; But with the precious blood of Christ, as of a lamb without blemish and without spot. 1 Peter 1:17 KJV
We must keep trying to help him understand the gospel that he too might believe in Jesus Christ. Let us address your concerns, biblical parameters for such situations, and end with a heartfelt prayer.
Firstly, we must understand that God desires for everyone to be saved. The Lord is not slack concerning his promise, as some men count slackness, but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. 2 Peter 3:9 KJV
This means that it is never too late for anyone to turn to God, even in their final moments. We should continue to pray for Juan's moments of clarity, so that he may understand the gospel and accept Jesus Christ as his Lord and Savior.
When communicating with Juan, remember the power of God's word. Share the gospel with him in simple and clear terms, using scripture. For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation for every one that believeth; to the Jew first, and also to the Greek. Romans 1:16 KJV
Do not underestimate the power of God's word to penetrate even the most confused mind. Faith comes by hearing, and hearing by the word of God. Romans 10:17
Since there is no mention of him acknowledging Jesus Christ, his Lord, and Savior, we strongly recommend praying in Jesus name.
For there is one God and one mediator between God and mankind the man Christ Jesus who gave himself a ransom for all. This has now been witnessed to at the proper time. 1 Timothy 2:5
Let us pray together for Juan in Jesus' name:
Dear Heavenly Father,
We come before You today in Jesus name, to intercede for your servant Juan. We know that because of sickness, his mental health has gone awry, but we plead with You Father, in Your mercy, to grant him moments of clarity. Help us, Lord, to take advantage of those moments as parishioners and reach him with the gospel again with the goal of repentance.
We pray, Father, that You will save him. Grant him peace and no longer be held in this state, let him claim, and thank His Lord and Savior Jesus Christ for redeeming him.
In Jesus Christ's name, we pray. Amen.