John Chrysostom — as excerpted in the Catena Aurea on Luke 3:3-6

“(ubi sup.) For as the sacrifice had not yet been offered up, nor had the holy Spirit descended, how could remission of sins be given? What is it then that St. Luke means by the words, for the remission of sins? Seeing the Jews were ignorant, and knew not the weight of their sins, and because this was the cause of their evils, in order that they might be convinced of their sins and seek a Redeemer, John came exhorting them to repentance, that being thereby made better and sorrowful for their sins, they might be ready to receive pardon. Rightly then after saying, that he came preaching the baptism of repentance, he adds, for the remission of sins. As if he should say, The reason by which he persuaded them to repent was, that thereby they would the more easily obtain subsequent pardon, believing on Christ. For if they were not led by repentance, in vain could they ask for grace, other than as a preparation for faith in Christ.”