G2435–ἱλαστήριος–hilastērios

Whom God has put forward as the sign of his mercy, through faith, by his blood, to make clear his righteousness when, in his pity, God let the sins of earlier times go without punishment;

ἱλαστήριον hilastērion “a propitiation”

And over it were the winged ones of glory with their wings covering the mercy-seat; about which it is not possible now to say anything in detail.

ἱλαστήριον, hilastērion “mercy seat,”