John Gill Commentary Nehemiah 3:15

"And the fountain gate repaired Shallun the son of Colhozeh, the ruler of the district of Mizpah; he built it, and covered it, and set up the doors thereof, the bolts thereof, and the bars thereof, and the wall of the pool of Shelah by the king`s garden, even unto the stairs that go down from the city of David." — Nehemiah 3:15 (ASV)

But the gate of the fountain
Of which see (Nehemiah 2:14)

repaired Shallum, the son of Colhozeh, the ruler of part of Mizpah ;
of a tract, district, town, or city so called; perhaps that in the tribe of Benjamin; see (Nehemiah 3:7) ,

he built it, and covered it ;
roofed it, which is not said of any of the other gates, whether because of the fountain at it:

and set up the doors thereof
finished it completely:

and the wall of the pool of Siloah, by the king's garden ;
which was formerly without the wall, on the west, but afterwards taken in by Manasseh, who built it; see (2 Chronicles 33:14) , and from hence the king's garden was watered:

and unto the stairs that go down from the city of David :
Zion, which was built on an eminence, from which they went down by steps into the lower city Acra.