Reply to Objection 5: Baptism derives its power from Christ's Passion, as a spiritual regeneration, with a spiritual death, of a previous life. Now "it is appointed unto man once to die" ( Heb. 9:27 ), and to be born once, wherefore man should be baptized but once. On the other hand, Penance derives its power from Christ's Passion, as a spiritual medicine, which can be repeated frequently.
Reply to Objection 6: According to Augustine (De vera et falsa Poenitentia, the authorship of which is unknown), "it is evident that sins displease God exceedingly, for He is always ready to destroy them, lest what He created should perish, and what He loved be lost," viz. by despair.