John Gill, on Neh 13:17

And it came to pass, that when the gates of Jerusalem began to be dark before the sabbath,.... Or "were shaded" (g); that is, as Jarchi interprets it, when the shadows of the eve of the sabbath were stretched out upon the gates; the sabbath did not begin till sun setting, and the stars appeared; but before that, as the sun was declining, the shadows through the houses in Jerusalem, and mountains about it, spread themselves over the gates: and when it was near dusk, and as soon as it was so, I commanded that the gates should be shut, and charged that they should not be opened till after the sabbath; until sun setting the next day: and some of my servants set I at the gates, that there should be burden brought in on the sabbath day; the porters being not to be trusted, being liable to be bribed and corrupted, which he knew his servants were not; and therefore, since it might be necessary on a few occasions to open the gates to let some persons in and out, and especially such who dwelt near, and came to worship, he placed his servants there, to take care that none were admitted that had any burdens upon them. (g) "obumbratae", Pagninus, Montanus; "obumbrarentur", Junius & Tremellius, Piscator, Rambachius; "incidentibus umbris", Tigurine version.