Gad was a Prophet during David’s Time. He was the one who informed David to return to the land of Judah while David was on the run from Saul.
On that day Gad went to David and said to him, “Go up and build an altar to the LORD on the threshing floor of Araunah the Jebusite.” 2 SAMUEL 24:18
As great as King David was, much of his greatness was no doubt due in part to the guidance of other spiritual leaders – leaders like Gad, the prophet.
Gad is referred to in the Bible as a “seer,” which is basically a prophet, someone who receives special messages from God. Gad appears to have been with David from his earliest days while he was on the run from Saul. He informed David not to stay in the stronghold (perhaps the fortress of Masada) and to return to the land of Judah (1 Samuel 22:5).
We don’t hear about Gad again until many years later, after David had been firmly established as king and had ordered a census to be taken throughout Israel. Gad informed David of the consequences of his actions and offered him three options for punishment. Gad also told David to build the altar (of the temple) on the place where the plague was stopped (2 Samuel 24).
It seems that Gad also helped David station where the various clans of Levites would be in the temple that David’s son Solomon would eventually build (2 Chronicles 29:25). Gad recorded many of the events of David’s reign so that others could read about them afterward for generations to come (1 Chronicles 29:29).
Another prophet who was closely linked with David’s reign was Nathan. He relayed the message that God planned to build David a lasting dynasty and that David’s son would build the temple (2 Samuel 7). Nathan was also the one who confronted David about his sin of adultery with Bathsheba (2 Samuel 12).