Ezra
1 Chronicles 12:16ESV·traditional attribution

And some of the men of Benjamin and Judah came to the stronghold to David.

Matthew Henry Presbyterian @wholebiblehenry

We have here an account of those that appeared and acted as David's friends, upon the death of Saul, to bring about the revolution. All the forces he had, while he was persecuted, was but 600 men, who served for his guards; but, when the time had come that he must begin to act offensively, Providence brought in more to his assistance.

Commenting on 1 Chronicles 12:1-22

John Gill Reformed Baptist @doctorgill

And there fell some of Manasseh to David,.... Of the tribe of Manasseh; they took his part, and on his side, and joined him: when he came with the Philistines against Saul to battle; which was a strong proof of their cordial attachment to him: but they helped them not: the Philistines; neither David nor his men, nor the Manassites that joined them: for the...

Jamieson-Fausset-Brown Reformed @jfbcommentary

the children of Benjamin and Judah--It is probable that the Benjamites invited the Judahites to accompany them, in order to prevent David being suspicious of them. Their anticipations, as the result showed, were well founded. He did suspect them, but the doubts of David as to their object in repairing to him, were promptly dispelled by Amasai or Amasa, who, by the secret impulse of...