Psalms 40:8

I delight Cp. Psalms 40:6. What is God's delight is his delight. Contrast the delight of the wicked in evil, Psalms 40:14.

thy will Thy good pleasure: what Thou approvest (Proverbs 15:8; Psalms 19:14).

thy law is within my heart Lit. in the midst of my body, as though God's law were itself the heart which gives life to his whole being (Psalms 22:14). Such was God's demand of Israel (Deuteronomy 6:6); such is the characteristic of the righteous (Psalms 37:31; Isaiah 51:7): such is to be the universal condition in the Messianic age (Jeremiah 31:33). The law will be graven not on tablets of stone (Exodus 32:15 f.), but on the tablet of the heart (Proverbs 3:3; Proverbs 7:3).

Psalms 40:6 a are quoted in Hebrews 10:5-7 according to the LXX [17], with some slight variations. The writer is contrasting Christ's perfect obedience with the inefficacy of the sacrifices of the Law, and he puts these words into His mouth as the most fitting expression of the purpose of His life. The willing obedience which the Psalmist of old was taught to recognise as the divine requirement for himself and Israel was carried to its completion, was -fulfilled," in Christ. The variation of the LXX from the Hebrew may seem to present a serious difficulty. But the appropriateness of the quotation does not depend on this particular clause, and the rendering of the LXX, whatever its origin, has in effect a sense analogous to the sense of the original. As the ear is the instrument for receiving the divine command, so the body is the instrument for fulfilling it. The possession of a body implies the duty of service, in the same way that the possession of hearing implies the duty of obedience. See Bp. Westcott's note.

[17] The reading of the LXX is σῶμα δὲ κατηρτίσω μοι, a body didst thou Prepare for me. This reading is attested by the Vulgate. Auresin the Gallican Psalter is a correction. καταρτίζεσθαι occurs in the LXX as the rendering of several Hebrew words, and might easily have been chosen to represent the obscure thou hart dug. -Body" for -ears" may then have been a free paraphrase. But the reading may have originated in an ancient corruption of the Greek text. Through a repetition of the final ϲ of the preceding word and the change of ⲰⲧⲓⲀ into ⲰⲘⲀ, Ⲏ θελ ⲎⲤⲀⲤ ω Ⲧⲓⲁ might easily have become Ⲏ θελ ⲎⲤⲀⲤⲤ ω ⲘⲀ.