John Gill Commentary Acts 10:3

"He saw in a vision openly, as it were about the ninth hour of the day, an angel of God coming in unto him, and saying to him, Cornelius." — Acts 10:3 (ASV)

He saw in a vision evidently
He was not in a dream, or in a trance, but he was thoroughly awake, and his eyes open, and was himself; it was not in the night, but in clear day:

about the ninth hour of the day ;
or three o'clock in the afternoon, which was the hour of prayer, (Acts 3:1) in which exercise he was now engaged, (Acts 10:30) at this time he saw

an angel of God coming to him ;
into the room where he was at prayer:

and saying unto him, Cornelius ;
he called him by his name, to let him know that he knew him, as angels are very knowing spirits; and to express his affection and friendship to him, and that he was a messenger, not of bad, but of good news to him; as well as to engage his attention to him; for he might be so intent at his devotion, that had he not called him by name, he would not have minded him.