1Jn 5, 16-17 There is sin that is not deadly

(1Jn 5, 16-17) There is sin that is not deadly
[16] If anyone sees his brother sinning, if the sin is not deadly, he should pray to God and he will give him life. This is only for those whose sin is not deadly. There is such a thing as deadly sin, about which I do not say that you should pray. [17] All wrongdoing is sin, but there is sin that is not deadly.

(CCC 1488) To the eyes of faith no evil is graver than sin and nothing has worse consequences for sinners themselves, for the Church, and for the whole world. (CCC 1864) “Therefore I tell you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven” (Mt 12:31; cf. Mk 3:29; Lk 12:10). There are no limits to the mercy of God, but anyone who deliberately refuses to accept his mercy by repenting, rejects the forgiveness of his sins and the salvation offered by the Holy Spirit (Cf. John Paul II, DeV 46). Such hardness of heart can lead to final impenitence and eternal loss. (CCC 1862) One commits venial sin when, in a less serious matter, he does not observe the standard prescribed by the moral law, or when he disobeys the moral law in a grave matter, but without full knowledge or without complete consent. (CCC 1863) Venial sin weakens charity; it manifests a disordered affection for created goods; it impedes the soul's progress in the exercise of the virtues and the practice of the moral good; it merits temporal punishment. Deliberate and unrepented venial sin disposes us little by little to commit mortal sin. However venial sin does not break the covenant with God. With God's grace it is humanly reparable. "Venial sin does not deprive the sinner of sanctifying grace, friendship with God, charity, and consequently eternal happiness" (John Paul II, RP 17 § 9). While he is in the flesh, man cannot help but have at least some light sins. But do not despise these sins which we call "light": if you take them for light when you weigh them, tremble when you count them. A number of light objects makes a great mass; a number of drops fills a river; a number of grains makes a heap. What then is our hope? Above all, confession… (St. Augustine, In ep. Jo. 1, 6: PL 35, 1982).