Albert Barnes Commentary Deuteronomy 25:13-19

"Thou shalt not have in thy bag diverse weights, a great and a small. Thou shalt not have in thy house diverse measures, a great and a small. A perfect and just weight shalt thou have; a perfect and just measure shalt thou have: that thy days may be long in the land which Jehovah thy God giveth thee. For all that do such things, [even] all that do unrighteously, are an abomination unto Jehovah thy God. Remember what Amalek did unto thee by the way as ye came forth out of Egypt; how he met thee by the way, and smote the hindmost of thee, all that were feeble behind thee, when thou wast faint and weary; and he feared not God. Therefore it shall be, when Jehovah thy God hath given thee rest from all thine enemies round about, in the land which Jehovah thy God giveth thee for an inheritance to possess it, that thou shalt blot out the remembrance of Amalek from under heaven; thou shalt not forget." — Deuteronomy 25:13-19 (ASV)

Honesty in trade, as a duty to our neighbor, is emphatically enforced once more . It is noteworthy that John the Baptist places similar duties at the forefront of his preaching (Compare to Luke 3:12 and following); and that “the prophets” (Amos 8:5; Micah 6:10–11) and “the Psalms” (Proverbs 16:11; Proverbs 20:10; Proverbs 20:23), no less than “the Law,” especially insist on them.

Diverse weights - that is, stones of unequal weights, the lighter to sell with, the heavier to buy with. Stones were used by the Jews instead of brass or lead for their weights, as they were less liable to lose anything through rust or wear.

It was not in keeping with the spirit or mission of the Law to aim at overcoming inveterate opposition by love and by attempts at conversion . The Law taught God’s hatred of sin and of rebellion against Him by commanding the extinction of the obstinate sinner.

The Amalekites were a related people (Genesis 36:15–16); and living as they did in the Sinai Peninsula, they must have known well the mighty acts God had done for His people in Egypt and the Red Sea. Yet they showed from the beginning a persistent hostility to Israel (Compare to Exodus 17:8, and note; Numbers 14:45). They therefore provoked the sentence pronounced here, which was finally executed by Saul (1 Samuel 15:3 and following).