Charles Ellicott Commentary 1 Chronicles 21:19

"And David went up at the saying of Gad, which he spake in the name of Jehovah." — 1 Chronicles 21:19 (ASV)

At the saying. —Samuel, according to. The difference is only that of the one tittle, or small projection, of a letter, mentioned in Matthew 5:18.

Which he spoke in the name of the Lord. —Samuel reads, as the Lord commanded. The variation is merely verbal.