Thou hast commanded - All this is here traced to the command of God; to the fact that he has required it. It is not mere human prudence; it is not mere morality; it is not because it will be for our interest; it is because God requires it. This is the foundation of all true virtue; and until a man acts from this motive it cannot be said that he is in the proper sense a righteous man.
To keep thy precepts diligently - Hebrew, "very much;" that is, to do it constantly; faithfully. Each one of his laws is to be observed, and to be observed always, and in all circumstances.

Thy precepts diligently - מאד meod, "superlatively, to the uttermost." God has never given a commandment, the observance of which he knew to be impossible. And to whatsoever he has commanded he requires obedience; and his grace is sufficient for us. We must not trifle with God.

Thou hast commanded us to keep thy precepts diligently. Here, and in the following verses, the psalmist expresses his great regard to the precepts, commandments, statutes, and judgments of God; and that as such, because they were commanded by him; were not the precepts of men, but the commands of God; who had a right to command, as Creator, Preserver, Redeemer, and King; and whose commands are not to be reckoned as indifferent things, that are at the option and choice of a creature, to be done or let alone at his pleasure; but are what God has enjoined, and are binding upon men; and which love should and does constrain the saints to have a regard unto, and to keep them diligently or vehemently; with all a man's might and strength, as the word is used in Deuteronomy 6:5. These are not at any time to be dispensed with, but, to be kept always constantly and steadily.

precepts--are those directions which relate to special conduct, from a word meaning "to inspect."
statutes--or ordinances, positive laws of permanent nature. Both words originally denote rather positive than moral laws, such as derive force from the divine appointment, whether their nature or the reasons for them are apprehended by us or not.
commandments--or institutions. The term is comprehensive, but rather denotes fundamental directions for conduct, both enjoining and forbidding.
have respect unto--or regard carefully as to their whole purport.