Then Joseph her husband, being a just man, and not willing to make her a public example, decided to put her away privately.
All Commentaries on Matthew 1:19 Go To Matthew 1
Augustine of Hippo
Serm. in App. s. 195: Joseph, understanding that Mary was with child, is perplexed that it should be thus with her whom he had received from the temple of the Lord, and had not yet known, and resolved within himself, saying, What shall I do? Shall I proclaim it, or shall I overlook it? If I proclaim it, I amindeed not consenting to the adultery; but I am running into the guilt of cruelty, for by Moses’ law she must be stoned. If I overlook it, I am consenting to the crime, and take my portion with the adulterers. Since then itis an evil to overlook the things, and worse to proclaim the adultery, I will put her away from being my wife.
Otherwise; if you alone have knowledge of a sin that any has committed against you, and desire to accuse him thereof before men, you do not herein correct, but rather betray him. But Joseph, “being a just man,” with great mercy spared his wife, in this great crime of which he suspected her. The seeming certainty of her unchastity tormented him, and yet because he alone knew of it, he was willing not to publish it, but to send her away privily; seeking rather the benefit than the punishment of the sinner.