Because, indeed, Moshiach suffered once on behalf of chatta'im (sins), a Tzaddik (righteous one) on behalf of the chote'im (unrighteous ones, sinners), that he might bring you to Hashem he, having been in the basar [TEHILLIM 16:9-10] put to death, yet, in the Ruach Hakodesh, having been made alive [4:6]; [see Isa 53:8]