Acts 2:27

εἰς ᾅδην, in Hades, i.e. in the unseen world. So too in Acts 2:31 where we have the more usual expression εἰς ᾅδου (understanding δόμον), but in the Psalm from which quotation is made, the best text of the LXX. gives the accusative there too.

δώσεις, Thou wilt suffer [lit. give].

τὸν ὅσιόν σου, Thy Holy One. The Hebrew word in the Psalm conveys the idea of beloved, as well as godly or pious.