Albert Barnes Commentary Nehemiah 13:15

"In those days saw I in Judah some men treading wine-presses on the sabbath, and bringing in sheaves, and lading asses [therewith]; as also wine, grapes, and figs, and all manner of burdens, which they brought into Jerusalem on the sabbath day: and I testified [against them] in the day wherein they sold victuals." — Nehemiah 13:15 (ASV)

The desecration of the Sabbath is first brought into prominence among the sins of the Jewish people by Jeremiah (Jeremiah 17:21–27). It inevitably gained ground during the captivity, when foreign masters would not have allowed the cessation of labor for one day in seven. On the return from the captivity, the sabbatical rest appears to have been one of the institutions most difficult to re-establish.

In the day - Some render, "concerning the day."