The Messiah would do God's (His Father) will.

OT Prophecy NT Fulfillment
Psalm 40:7-8
"[7] Then said I, Lo, I come: in the volume of the book it is written of me, [8] I delight to do thy will, O my God: yea, thy law is within my heart."
John 5:30
"I can of mine own self do nothing: as I hear, I judge: and my judgment is just; because I seek not mine own will, but the will of the Father which hath sent me."

Tanakh - Ketuvim - Psalm 40:8-9

"[8] Then said I: 'Lo, I am come with the roll of a book which is prescribed for me; [9] I delight to do Thy will, O my G-d; yea, Thy law is in my inmost parts."

Hebrew OT - Psalms 40:8-9

.ילע בותכ רפס-תלגמב יתאב-הנה יתרמא זא   [8]
.יעמ ךותב ךתרותו יתצפח יהלא ךנוצר-תושעל   [9]

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