Both Matthew and Mark use ἰσχύοντες, the strong. This use of the verb in its primary sense, to be in sound health, is found in Luk 7:10; Luk 15:27; and once in John, 3 Ep. 3Jo 1:2. For this meaning it is the regular word in medical writings. Paul uses it only in the metaphorical sense: sound doctrine, sound words, sound in faith, etc. See 1Ti 1:10; 1Ti 6:3; Tit 1:13, etc.