Let us hear the conclusion of the whole matter: Fear God, and keep his commandments: for this is the whole duty of man. For God shall bring every work into judgment, with every secret thing, whether it be good, or whether it be evil.
Deuteronomy 6:1-2
Now these are the commandments, the statutes, and the judgments, which the LORD your God commanded to teach you, that ye might do them in the land whither ye go to possess it: That thou mightest fear the LORD thy God, to keep all his statutes and his commandments, which I command thee, thou, and thy son, and thy son's son, all the days of thy life; and that thy days may be prolonged.
Ecclesiastes 12:13 closes the entire book with the Deuteronomy 6 fear-and-keep-commandments formula as the summary of human duty. Deuteronomy 6 established this exact pairing — fear the LORD, keep all his statutes and commandments — as the purpose of all Torah teaching, binding every generation across all the days of their lives. The Preacher arrives at the same constitutional conclusion through experiential wisdom inquiry as Moses arrived at through divine covenant revelation: fear God and keep his commandments is the whole of human duty.