on Mortal and Venial Sin

Tertullian On Modesty ch 21 [160-240 AD]
"Discipline governs a man, power sets a seal upon him; apart from the fact that power is the Spirit, but the Spirit is God. What, moreover, used [the Spirit] to teach? That there must be no communicating with the works of darkness. Observe what he bids. Who, moreover, was able to forgive sins? This is his alone prerogative: for 'who remits sins but God alone?' and, of course, [who but he can remit] mortal sins, such as have been committed against himself and against his temple?"