In the volume of the book it is written of Me… – Psalm 40:7; Hebrews 10:7

There was a time before all time, when there was no day but the Ancient of Days, when all that existed was the Lord, who is all in all: then the sacred Three entered into covenant, in mutual agreement, for a sublime end. Man sinning, the Son of God shall be the surety. Christ shall bear the result of man’s offense; He shall vindicate the law of God, and make Jehovah’s name more glorious than ever it has been. The second person of the divine Unity was pledged to come, and take up the nature of men, and so become the firstborn among many brethren to lift up a fallen race, and to save a number that no man can number, elect of God the Father, and given to the Son to be His heritage, His portion, His bride. Then did the Well-beloved strike hands with the eternal God, and enter into covenant engagements on our behalf: “In the volume of the book it is written.” That sealed book, upon whose secrets no angel’s eye has looked, a book written by the finger of God long before He wrote the Book of the law upon tables of stone, that book of God may be spoken of in the Psalm, “And in Thy book all My members were written, which in continuance were fashioned, when as yet there was none of them.” Our Lord came to carry out all His suretyship engagements: His work is the exact fulfillment of His engagements recorded in the eternal covenant, “ordered in all things and sure.” He acts out every mysterious line and syllable, even to the full. Then He said, “A body hast Thou prepared Me. Lo, I come: in the volume of the book it is written of Me.” It is ever a pleasing study to see our Lord, both in the written Word, and in the eternal covenant of grace. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2202.cfm