Please reread the catechism, and perhaps talk to a priest…
To paraphrase a prominent contemporary theologian: ‘Use the Bible only on thyself…’
The Catechism states masturbation, under the three conditions is a mortal sin. And is always grave matter.
Pope John Paul II said about the Catechism: “I put my apostolic authority on this work.”
If you want an exact quote:
2352: “By masturbation is to be understood the deliberate stimulation of the genital organs in order to derive sexual pleasure. ‘Both the Magisterium of the Church, in the course of a constant tradition, and the moral sense of the faithful have been in no doubt and have firmly maintained that masturbation is an intrinsically and gravely disordered action.’ ‘The deliberate use of the sexual faculty, for whatever reason, outside of marriage is essentially contrary to its purpose.’ For here sexual pleasure is sought outside of ‘the sexual relationship which is demanded by the moral order and in which the total meaning of mutual self-giving and human procreation in the context of true love is achieved’.”
“To form an equitable judgment about the subjects’ moral responsibility and to guide pastoral action, one must take into account the affective immaturity, force of acquired habit, conditions of anxiety or other psychological or social factors that lessen, if not even reduce to a minimum, moral culpability.”
Prior to Persona humana, the Magisterium had condemned masturbation on multiple occasions. In his 1054 letter to St. Peter Damian, Pope Leo IX censured, inter alia, the shameful deed of those who brought forth the seed “by their own hands” (propriis manibus; Denzinger-Hünermann [Denz.-H] 2010, 688). In 1665 the Holy Office referred to the sin of “pollution” — with the clear implication of masturbation (Denz.-H 2010, 2044). In 1929 the same Holy Office rejected recourse to masturbation for obtaining a medical specimen of sperm (Denz.-H 2010, 2044). Pope Pius XII reaffirmed the condemnation of masturbation — even when done for medical purposes — in 1953 and 1956 (cf. Acta apostolicae sedis [AAS] 45 [1953] 678 and AAS 48 [1956] 472-473). In 1952 he also rejected the argument that sins of masturbation during adolescence do not constitute a grave matter (AAS 44 [1952], 275-276).
Masturbation is not mentioned by name in either the Old or New Testament. Some theologians have associated it with the sin of Onan, who practiced withdrawal to avoid fulfilling his duty to his brother’s widow (Gen. 38:8-10). Others have tried to associate masturbation with one of the sins listed by St. Paul in I Corinthians 6:9 (sexual immorality, idolatry, adultery, male prostitution, homosexual offenses) or in Galatians 5:19-21 (adultery, fornication, uncleanness, lasciviousness). A direct prohibition of deliberately engaging in sexual fantasy is also included; in Matthew 5:28 Jesus says, “Everyone who looks at a woman lustfully has already committed adultery with her in his heart.” The act of willful masturbation virtually always involves sexual fantasy and often involves the use of pornography, thus coming under the prohibition against adultery in the heart.
The Church teaches that masturbation is driven by lust (epithumeo), and the scriptural warnings against lust are clear and unequivocal, such as in these passages:
For this is the will of God, your sanctification: that you should abstain from sexual immorality, that each of you should know how to possess his own vessel in sanctification and honor, not in passion of lust, like the Gentiles who do not know God (1 Thess 4:3-5).
Beloved, I beg you as sojourners and pilgrims, abstain from fleshly lusts which war against the soul (1 Pet 2:11).
Let us walk properly, as in the day, not in revelry and drunkenness, not in lewdness and lust … But put on the Lord Jesus Christ, and make no provision for the flesh, to fulfill its lusts (Rom 13:13-14).
But fornication, and all uncleanness, let it not be once named among you, as becomes saints; neither filthiness. For it is a shame to [even] speak of those things which are done of them in secret, let alone do them (Eph 5:3, 12). For if you live according to the flesh you will die; but if by the Spirit you put to death the misdeeds of the body, you will live (Rom 8:13).
Being a “grave moral disorder” and “an intrinsically and gravely disordered action” the Church teaches that even a single act of masturbation can theoretically send a person to Hell for all eternity
In order to be a mortal sin, two additional factors must be present:
The person must commit the act with full knowledge of the sin and of its seriousness.
“It must be committed with deliberate and complete consent.”
This sin cannot be committed by accident.
Full knowledge means it’s a mortal sin.
