John 1:37

Heard him speak

(ηκουσαν αυτου λαλουντος). First active indicative of ακουω and present active participle of λαλεω in genitive case agreeing with αυτου, object of ακουω. "Heard him speaking" (kind of indirect discourse). John had disciples (μαθητα, learners, from μανθανω, to learn).They followed Jesus

(ηκολουθησαν τω Ιησου). Associative instrumental case after verb (first aorist active indicative, ingressive aorist, of ακολουθεω). These two disciples of the Baptist (Andrew and John) took him at his word and acted on it. John the Baptist had predicted and portrayed the Messiah, had baptized him, had interpreted him, and now for the second time had identified him.