Then (tote). When it was plain that God could not be propitiated by such sacrifices.
Lo, I am come (Idou hēkō). The Messiah is represented as offering himself to do God’s will (tou poiēsai to thelēma sou, the genitive articular infinitive of purpose).
In the roll of the book it is written of me (en kephalidi bibliou gegraptai peri emou). Stands written (gegraptai, perfect passive indicative). Kephalis is a diminutive of kephalē (head), a little head, then roll only here in N.T., but in the papyri. Here it refers “to the O.T. as a prediction of Christ’s higher sacrifice” (Moffatt).