Imperfect tense. They kept watching. The compound verb, with παρά, by the side of, means to watch carefully or closely, as one who dogs another's steps, keeping beside or near him. Wyc., They aspieden him: i.e., played the spy. On τηρέω, to watch, see on Joh 17:12.
He would heal (θεραπεύσει)
Future tense: whether he will heal, the reader being placed at the time of the watching, and looking forward to the future.