Mark 9:20

ἰδὼν may be taken as referring to the boy (Schanz), in which case we should have an anacolouthistic nominative for the accusative, the writer having in view to express his meaning in passives (ἐκυλίετο); or to the spirit (πνεῦμα) by a construction ad sensum = the spirit seeing Jesus made a last attack (Weiss in Meyer, et al.). This is most in keeping with the mode of conceiving the matter natural to the evangelist. The visible fact was a fresh fit, and the explanation, from the possession point of view, that the spirit, seeing Jesus, and knowing that his power was at an end, made a final assault.