In mortal sin according to ‘‘My Catholic Faith’’ all our good works (including prayers) give us no merit. However, are we able to still pray for others to save their souls or offer up prayers for them? Or would this be futile if one was in a state of mortal sin?
I would still do it. That doesn’t excuse you from going to confession, if you are able.
Sr. Josefa Menendez (1890-1923) -Jesus’ Message to the World of His Mercy for All
“I would like these [those living with sin] to understand that it is not the fact of being in sin that ought to keep them from Me. They must never think that there is no remedy for them, nor that they have forfeited for ever the love that once was theirs… No, poor souls, the God who has shed all His Blood for you has no such feelings for you!”
“It is My intention also, to show souls that I never refuse grace, even to those who are guilty of grave sin; nor do I separate them from the good souls whom I love with predilection. I keep them all in My Heart, that all may receive the help needed for their state of soul.” -Jesus to Sr. Josefa Menendez
Nobody can pray anything without God participating and urging it, first. So if you want to pray while in mortal sin, obviously the Holy Spirit wants you to pray.
But go to Confession as soon as you can.
When we are in the state of mortal sin it is us who rejected God. God never rejects us. If we are prompted to pray for someome then our reuniting with God already began. Get to confession but never believe that God refuses to hear us nor does He ignore our prayers if we are truly repentant. Refer to the awesome story of the Prodigal Son in Luke. God is waiting for us to return.
Not only is it useful to pray for one in Mortal Sin, but it is also important because those who are in Mortal Sin are the ones who need prayers the most.