36 But according to the Scriptures we have been taught that death is threefold. One death is when we die to sin, but live to God. Blessed, then, is that death which, escaping from sin, and devoted to God, separates us from what is mortal and consecrates us to Him Who is immortal. Another death is the departure from this life, as the patriarch Abraham died, and the patriarch David, and were buried with their fathers; when the soul is set free from the bonds of the body. The third death is that of which it is said: “Leave the dead to bury their own dead.” In that death not only the flesh but also the soul dies, for “the soul that sins, it shall die.” For it dies to the Lord, through the weakness not of nature but of guilt. But this death is not the discharge from this life, but a fall through error.
Source: On the Death of Satyrus (New Advent)