All recent commentators seem to be agreed that the words "to Shuppim" ought to be cancelled, the name having arisen from an accidental repetition of the preceding word, "Asuppim."
The gate Shallecheth - literally, "the gate of projection" - the gate, i. e., through which were "thrown out" the sweepings of the temple, the ashes, the offal of the victims, and the like.
The causeway of the going up - Compare the marginal reference note.
Ward against ward - Or, "watch opposite to watch." Hosah had in charge both the western gate of the temple, and also the gate Shallecheth, which was in the outer wall, opposite. Hence, he had to keep two watches, one over against the other.

The gate Shallecheth - The gate of the projections: probably that through which all the offal of the temple was carried out.

To Shuppim and Hosah [the lot came forth] westward, with the gate (h) Shallecheth, by the causeway of the going up, ward against ward.
(h) At which they used to cast out the filth of the city.

To Shuppim and Hosah the lot came forth westward,.... Of Shuppim no mention is before made; of Hosah, see 1-Chronicles 26:10 their lot was to be placed at the gates on the western wall, where were four; the two more southward being assigned to the sons of Obededom, whose lot also was southward, are taken notice of under the division in the preceding verse; Parbar was another, 1-Chronicles 26:18, and another follows here:
with the gate Shallecheth, by the causeway of the going up; this gate was in later times called Coponius, from the name of a Roman commander, in the times of Herod, who might give it this name on his account; it might have the name of Shallecheth either from "sending out", or carrying out the filth of the temple through it; or rather from "casting up the causeway", as here expressed, which was the going up, or ascent, Solomon made, by which he went up to the temple, 1-Kings 20:5 and which agrees with the description Josephus (a) gives of one of the gates on the western wall, that it led to the royal palace, the valley between being filled up for the passage; on each side of which causeway, it is said, grew oaks and teil trees, see Isaiah 6:13 which served both to keep up the causeway, and to make a fine, pleasant, shady walk for the king to pass through to the temple; all which are observed by Dr. Lightfoot (b):
ward against ward; for as the gates answered one another, so the wards or watches at them.
(a) Antiqu. l. 15. c. 11. sect. 5. (b) Ut supra, (Prospect of the Temple), c. 5. sect. 1.

the gate Shallecheth--probably the rubbish gate, through which all the accumulated filth and sweepings of the temple and its courts were poured out.
by the causeway of the going up--probably the ascending road which was cast up or raised from the deep valley between Mount Zion and Moriah, for the royal egress to the place of worship (2-Chronicles 9:4).
ward against ward--Some refer these words to Shuppim and Hosah, whose duty it was to watch both the western gate and the gate Shallecheth, which was opposite, while others take it as a general statement applicable to all the guards, and intended to intimate that they were posted at regular distances from each other, or that they all mounted and relieved guard at the same time in uniform order.

The word לשׁפּים is unintelligible, and probably has come into the text merely by a repetition of the two last syllables of the preceding word, since the name שׁפּים (1-Chronicles 7:12) has no connection with this passage. To Hosah fell the lot towards the west, by the door Shallecheth on the ascending highway. העולה המסלּה is the way which led from the lower city up to the more lofty temple site. Instead of the door on this highway, in 1-Chronicles 26:18, in the statement as to the distribution of the guard-stations, Parbar is named, and the highway distinguished from it, four doorkeepers being appointed for the מסלּה, and two for פּרבּר. פּרבּר .פּר, probably identical with פּרורים, 2-Kings 23:11, a word of uncertain meaning, was the name of an out-building on the western side, the back of the outer court of the temple by the door Shallecheth, which contained cells for the laying up of temple goods and furniture. שׁלּכת, Bttcher translates, Proben, S. 347, "refuse-door;" see on 2-Kings 23:11. Nothing more definite can be said of it, unless we hold, with Thenius on 2-Kings 23:11, that Ezekiel's temple is in all its details a copy of the Solomonic temple, and use it, in an unjustifiable way, as a source of information as to the prae-exilic temple. משׁמר לעמּת משׁמר (as in Nehemiah 12:24), guard with (over against?) guard, or one guard as the other (cf. on לעמּת, 1-Chronicles 26:12 and 1-Chronicles 25:8), Bertheau connects with Hosah, according to the Masoretic punctuation, and explains it thus: "Because it was Hosah's duty to set guards before the western gate of the temple, and also before the gate Shallecheth, which lay over against it." Clericus, on the contrary, refers the words to all the guard-stations: cum ad omnes januas essent custodiae, sibi ex adverso respondebant. This reference, according to which the words belong to what follows, and introduce the statement as to the number of guards at the individual posts which follows in 1-Chronicles 26:17., seems to deserve the preference. So much is certain in any case, that there is no ground in the text for distinguishing the gate Shallecheth from the western gate of the temple, for the two gates are not distinguished either in 1-Chronicles 26:16 or in 1-Chronicles 26:18.

Shallecheth - A gate of the court so called, as some think, because the ashes and filth of the temple were cast out on that side, which was the most convenient for that purpose, because that was a private quarter, the great ways to the temple lying on the other sides. Going up - By which causeway they went up towards the temple. Ward against ward - As one gate was over against another, the west against the east, and the north against the south, so one ward was over against another.