He gathered... and passed. — David, hearing of the great Syrian rally, now took the field in person. Joab may have been with him, but more probably was employed at the south in holding the Ammonites in check and preventing their forming a junction with their confederates.
Related Commentaries of 2 Samuel 10:17
2 Samuel 10:17
17 And when it was told David, he gathered all Israel together, and passed over Jordan, and came to Helam. And the Syrians set themselves in array against David, and fought with him.