He does not recommend SOMEONE ELSE to pray for mortal sin.
he is saying we can pray for other poeple’s venial sin, and they will be forginven, but that does not work for mortal sin.
He is not saying you YOURSELF cant pray for your sins.
Furthermore, Jesus teached us to pray for our sins on the LORD prayer.
John isn’t restricting the point he’s making
16 If any one sees his brother committing what is not a mortal sin, he will ask, and God will give him life for those whose sin is not mortal. There is sin which is mortal;
I do not say that one is to pray for that. 17 All wrongdoing is sin, but there is sin which is not mortal.
John is saying, Prayer alone, is not enough when it comes to the forgiveness of mortal sin.
So How does the Church look at it?
the following examples from the CCC show, in the case of repentance of mortal sin, not to depend exclusively on personal feelings of remorse . Maybe one thinks it’s deep contrition when it isn’t… Perfect contrition may not have happened, that’s why Jesus established a supernatural sacrament so we do things His way, that He established, … not depend on one’s personal far less than perfect emotional state at the moment of contrition.
Examples: From the Catechism on this subject
#1395 CCC
the forgiveness of mortal sins - that is proper to the
sacrament of Reconciliation.
#1457 CCC
Anyone who is aware of having committed a mortal sin must not receive Holy Communion,
even if he experiences deep contrition, without having first received sacramental absolution, unless he has a grave reason for receiving Communion and there is no possibility of going to confession.
I.E. the Church warns against one depending on their contrition for forgiveness, as if they think it is perfect when it may NOT be
#1440
At the same time it (mortal sin) damages communion with the Church. For this reason conversion entails both God’s forgiveness and reconciliation with the Church, which are expressed and accomplished liturgically bythe sacrament of Penance and Reconciliation.
(Protestants are outside the Church. they can’t walk off the street and go to reconciliation)
#1445
“The words
bind and loose mean: whomever you exclude from your communion, will be excluded from communion with God; whomever you receive anew into your communion, God will welcome back into his.
Reconciliation with the Church is inseparable from reconciliation with God.”
That makes the point much bigger
#1497
Individual and integral confession of grave sins followed by absolution remains the only ordinary means of reconciliation with God and with the Church.
#1856
Mortal sin, by attacking the vital principle within us - that is, charity - necessitates a new initiative of God’s mercy and a conversion of heart which is normally accomplished within the setting of the sacrament of reconciliation:
Q:
So to the topic, Protestants are outside the Church. So what do THEY do for assurance their mortal sins are forgiven?