20. ἐθαύμασαν. It was rather the power and wonder of the act than the deeper significance of it that moved the disciples. The miracle was to them an ‘act of power’ (δύναμις), or a ‘wonder’ (τέρας), rather than a ‘sign’ (σημεῖον). Yet Jesus follows the turn their thoughts take, and teaches that prayer and faith will remove mountains of difficulty, see ch. Mat 17:20.