Matthew 5:47 - Ellicott's Commentary On The Whole Bible

If ye salute your brethren. — The prominence of salutation in the social life of the East gives a special vividness to this precept. To utter the formal “Peace be with you,” to follow that up by manifold compliments and wishes, was to recognise those whom men saluted as friends and brothers. But this the very heathen did (heathen rather than “publicans” being here the true reading): were the followers of Christ to be content with copying heathen customs?