7 “And the house was filled with the odor.” The world is filled with the fame of a good character: for a good character is as a pleasant odor. Those who live wickedly and bear the name of Christians, do injury to Christ: of such it is said, that through them “the name of the Lord is blasphemed.” If through such God's name is blasphemed, through the good the name of the Lord is honored. Listen to the apostle, when he says, “We are a sweet savor of Christ in every place.”
As it is said also in the Song of Songs, “Your name is as ointment poured forth.” Attend again to the apostle: “We are a sweet savor,” he says, “of Christ in every place, both in them that are saved, and in them that perish. To the one we are the savor of life unto life, to the other the savor of death unto death: and who is sufficient for these things?” The lesson of the holy Gospel before us affords us the opportunity of so speaking of that savor, that we on our part may give worthy utterance, and you diligent heed, to what is thus expressed by the apostle himself, “And who is sufficient for these things?”
But have we any reason to infer from these words that we are qualified to attempt speaking on such a subject, or you to hear? We, indeed, are not so; but He is sufficient, who is pleased to speak by us what it may be for your profit to hear. The apostle, you see, is, as he calls himself, “a sweet savor:” but that sweet savor is “to some the savor of life unto life, and to others the savor of death unto death;” and yet all the while “a sweet savor” in itself. For he does not say, does he, To some we are a sweet savor unto life, to others an evil savor unto death?
He called himself a sweet savor, not an evil; and represented himself as the same sweet savor, to some unto life, to others unto death. Happy they who find life in this sweet savor! But what misery can be greater than theirs, to whom the sweet savor is the messenger of death?
Source: Tractates on the Gospel of John (New Advent)