A.T. Robertson Commentary Acts 1:9

"And when he had said these things, as they were looking, he was taken up; and a cloud received him out of their sight." — Acts 1:9 (ASV)

As they were looking (βλεποντων αυτων). Genitive absolute. The present participle accents the fact that they were looking directly at Jesus.

He was taken up (ep rth). First aorist passive indicative of επαιρω, old and common verb meaning to lift up. In Lu 24:51 we have "he was borne up" (ανεφερετο) and in Ac 1:2, 1:11; 1 Timothy 3:6 "was received up" (ανελημπθη).

Received (υπελαβεν). Second aorist active indicative of υπολαμβανω, literally here "took under him." He seemed to be supported by the cloud. "In glory" Paul adds in 1 Timothy 3:16.

Out of their sight (απο των οφθαλμων αυτων). From their eyes (απο with ablative case).