There was something fundamentally anomalous about their gazing up into the sky when they had been commissioned to go to the ends of the earth. It was the earth not the sky which was to be their preoccupation. Their calling was to be witnesses not stargazers. The vision they were to cultivate was not upwards in nostalgia to the heaven which had received Jesus, but outwards in compassion to a lost world which needed him. It is the same for us…
We need to hear the implied message of the angels: ‘You have seen him go. You will see him come. But between that going and coming there must be another. The Spirit must come, and you must go— into the world for Christ’….
–From his commentary on Acts, cited by yours truly in the morning sermon