That he should offer himself often (ινα πολλακις προσφερη εαυτον). Purpose clause with ινα and present active subjunctive of προσφερω (keep on offering himself, like Hebrews 5:1; Hebrews 5:3).

With blood not his own (εν αιματ αλλοτριω). So-called instrumental use of εν (accompaniment). αλλοτριος means "belonging to another," "not one's own" (Luke 16:12).