John Gill Commentary Nehemiah 8:11

"So the Levites stilled all the people, saying, Hold your peace, for the day is holy; neither be ye grieved." — Nehemiah 8:11 (ASV)

So the Levites stilled all the people
Made them quiet and easy, being backed by the governor:

saying, hold your peace ;
refrain from weeping and mourning:

for the day is holy ;
a festival, set apart for joy and gladness:

neither be you grieved ;
inwardly; as they were not to show any signs of sorrow outwardly, so they were not to cherish grief inwardly.