it is right there in Heb 2.14-15, but the context of 2.5-18 is also important. (And in 2.17 the English word propitiation - made up by Tyndale, I believe - or even expiation is flat-out wrong; in Greek it is enter into the mercy-seat.)Finally, in the New English Translation of the Septuagint, Jer 17.9-10 reads, The heart is deep above all else, and so is a man, and who shall understand him?