Gregory the Great — as excerpted in the Catena Aurea on Matthew 12:31-32

“(Dial. iv. 39.) Hence we may gather that there are some sins that are remitted in this world, and some in the world to come; for what is denied of one sin, must be supposed to be admitted of others. And this may be believed in the case of trifling faults; such as much idle discourse, immoderate laughter, or the sin of carefulness in our worldly affairs, which indeed can hardly be managed without sin even by one who knows how he ought to avoid sin; or sins through ignorance (if they be lesser sins) which burden us even after death, if they have not been remitted to us while yet in this life. But it should be known that none will there obtain any purgation even of the least sin, but he who by good actions has merited the same in this life.”