William Burkitt on Matthew 1:19

That is, being an holy person, and a strict observer of the rites of his nation, he was unwilling to accompany with a defiled woman, and therefore minded to put her away, by giving a bill of divorce into her hand before two witnesses; but being kind and gentle, he intended to put her away privily, lest she should have be exposed and stoned to death.

Observe here, How early our dear Lord's sufferings began; he and his mother are designed to be put away, even when he was but an embryo in the womb.

Observe further, from the great clemency of Joseph towards the suspected virgin, that kind and merciful men always presume the best, and prosecute with gentleness, especially where life is concerned. Meek Joseph doth resolve upon the milder course, and chooses rather to put her away privily, than publicly to expose her. Lev 19:20; Gen 6:9; 38:24; Deut 24:1-4