15. This verse and the beginning of Enoch's prophecy is composed in Hebrew poetic parallelism, the oldest specimen extant. Some think Lamech's speech, which is also in poetic parallelism, was composed in mockery of Enoch's prophecy: as Enoch foretold Jehovah's coming to judgment, so Lamech presumes on impunity in polygamy and murder (just as Cain the murderer seemed to escape with impunity).
convince—convict.
hard speeches—such as are noticed in Jude 8, 10, 16; Mal 3:13, 14; contrast Ro 16:17.
ungodly sinners—not merely sinners, but proud despisers of God: impious.
against him—They who speak against God's children are regarded by God as speaking against Himself.