Psalms 40:7

Then said I: i.e. at Incarnation, when He "came into the world" (Hebrews 10:5 ).

volume of the book = scroll, that is to say, the book. Genitive of Apposition, and Figure of speech Pleonasm ( App-6 ) = the book of the law ( App-47 ).

it is written = it is prescribed. Compare 2 Kings 22:13 .

of me = for me. Joseph and Mary should have remembered what was "written" (Luke 2:49 ).