Prophet Gad

Gad, called "the prophet" and "David's seer", first appears when David was hiding in the stronghold: Gad told him to leave and go into the land of Judah (1 Samuel 22:5). Decades later, after David ordered a census of the people, Gad brought him three choices of punishment: years of famine, three months fleeing before his enemies, or three days of plague. David answered, "Let us fall into the hand of the LORD, for His mercies are great." After the plague, Gad told him to build an altar on the threshing floor of Araunah the Jebusite, which David bought, the future site of the Temple (2 Samuel 24).

According to 2 Chronicles 29:25, the Levites' music in the Temple followed the commandment of David, Gad and Nathan. 1 Chronicles 29:29 cites "the records of Gad the seer" as a source for David's reign, and the Talmud (Bava Batra 15a) says Gad and Nathan completed the book of Samuel.