Charles Ellicott Commentary 1 Chronicles 21:9

"And Jehovah spake unto Gad, David`s seer, saying," — 1 Chronicles 21:9 (ASV)

And the Lord (Jehovah) spoke to Gad. —Samuel, “And David arose in the morning. Now a word of Jehovah had come to Gad the prophet, a seer of David, saying—” This appears to be more original than our text.

David’s seer. —Better, a seer of David’s, for the same title is applied to Heman (1 Chronicles 25:5). For Gad, see 1 Samuel 22:5, and 1 Chronicles 29:29. From the latter passage it has been inferred that it was Gad who wrote the original record of the census.