Angels told the apostles that Jesus would return later.

Acts 1:10-11

10 While the apostles were still staring towards the sky as he was going up, suddenly two men who were wearing white clothes stood beside them. They were angels. 11 One of them said, “You men from Galilee district, ◄you do not need to stand here any longer looking up at the sky!/why do you still stand here looking up at the sky?► [RHQ] Some day this same Jesus, whom God took from you up to heaven, will come back to earth. He will return in the same manner as you just now saw him when he went up to heaven, but he will not return now.”