'Rest In Peace' is what we last wish for our loved ones when they have finished their earthly journey. We pray that the Lord will embrace them and give them peace and love as they desired to serve the Lord in their life and now is the time for them to rest in God's love.
'Rest in Peace' makes sense for those who have faith in Jesus, in this life and in the life to come, because their lives are guided, not by the urge of the flesh, but by the Spirit of the Risen Christ. St. Paul wrote to the Romans 8,9 that when the Spirit of God made home in us we belong, not to the flesh, but to the Spirit. The Spirit has raised Jesus from death; it is the same Spirit will sustain the life to those who belong to her. It is the Spirit that Jesus said God the Father revealed to mere children- Mat 11,25. Simple minded children are those who accept Jesus as their Lord and learnt from Him. The more we question about the faith in Jesus the more we complicate the faith Jesus was teaching about. A human mind prefers logical thinking and faith is the mystery of God's love and love has its own way of operation, the way of a heart not of a mind. The very first step of faith begins with loving God and loving others and that will help to deepen our faith in Christ. Love one another is the way of the Lord. Through providing services and charity we learn that love is the key to unlock the mystery of God's love. Children could never understand how much parents love them. The cross is the visible sign of God's love for us and we would never understand the mystery of the cross. Experiencing God's love helps us to live a life of thankfulness and acknowledge that without God we are nothing. We don't even exist.
Denying the faith Jesus offers we gain nothing. However accepting the faith Jesus offers we gain everything. We gain hope and love and everlasting life. Denying Jesus St Paul said that person lives according to the flesh. We understand that no matter how much we care for the flesh it is fading away and eventually death. Without faith in Jesus the final wish for our love ones 'Rest In Peace' needs some explanation. Who and what would give guarantee that the deceased will 'Rest In Peace' or it is just a mere wish. We certainly don't want to give our love ones something which we believe it is unreal.
I can't prove that the God I believe in exists and equally you can't prove that there is no God but the faith I have in Jesus gives meanings for most things I do and say now and after and that simplifies life. While denying the existence of God we struggle to find answers for things. Science has answers for many things but they are not the final ones because new findings give new answers. There is no burden which is heavier and last longer than to say good bye to the loved ones and Jesus calls us to him for support when he says: come to me all who are heavy burden and rest in me Mt 11,30.