Unto thousands - unto the thousandth generation. Yahweh's visitations of chastisement extend to the third and fourth generation, his visitations of mercy to the thousandth; that is, forever. That this is the true rendering seems to follow from Deuteronomy 7:9; Compare 2-Samuel 7:15-16.

And showing mercy unto thousands - Mark; even those who love God and keep his commandments merit nothing from him, and therefore the salvation and blessedness which these enjoy come from the mercy of God: Showing mercy, etc. What a disproportion between the works of justice and mercy! Justice works to the third or fourth, mercy to thousands of generations! The heathen had maxims like these. Theocritus also teaches that the children of the good shall be blessed because of their parents' piety, and that evil shall come upon the offspring of the wicked: -
Ευσεβεων παιδεσσι τα λωΐα, δυσσεβεων δ' ου.
Idyll. 26, v. 32.
Upon the children of the righteous fall
The choicest blessings; on the wicked, wo.
That love me, and keep my commandments - It was this that caused Christ to comprise the fulfillment of the whole law in love to God and man; see Clarke's note on Exodus 20:1. And as love is the grand principle of obedience, and the only incentive to it, so there can be no obedience without it. It would be more easy even in Egyptian bondage to make brick without straw, than to do the will of God unless his love be shed abroad in the heart of the Holy Spirit. Love, says the apostle, is the fulfilling of the law; Romans 13:10.

And shewing mercy unto (e) thousands of them that love me, and keep my commandments.
(e) So ready is he rather to show mercy than to punish.

And showing mercy unto thousands of them that love me,.... And show their love by worshipping God, and him only, by serving him acceptably with reverence and godly fear, by a cheerful obedience to all his commands, by all religious exercises, both internal and external, as follows:
and keep my commandments; not only this, but all others; for keeping these from right principles, and with right views, is an instance and evidence of love to God, see John 14:15 and to such persons he shows mercy and kindness, performs acts of grace, and bestows on them blessings of goodness; and indeed it is owing to his own grace, mercy, and kindness to them, that they do love him, and from a principle of love observe his precepts; and this is shown to thousands, to multitudes, who are blessed with such grace as to love the Lord, and keep his commandments: though rather this is to be understood of a thousand generations, and not persons, and should have been supplied, as in the preceding verse, "unto a thousand generations", God being more abundant in showing mercy, and exercising grace and goodness, than he is rigorous in inflicting punishment.