Psalm 73 in the Septuagint (where it is numbered Psalm 72) contains an unusual metaphor for apostasy:
οτι ιδου οι μακρυνοντες εαυτους απο σου απολουνται εξωλεθρευσας παντα τον πορνευοντα απο σου
For behold those who remove themselves from thee are lost; thou shalt destroy all those who fornicate from thee (Psalm 72:27 LXX).
This is actually a fairly close translation of the Hebrew. In the minds of the ancient Israelites immorality and apostasy are closely linked (see also Hosea).