John Gill Commentary Nehemiah 4:20

"in what place soever ye hear the sound of the trumpet, resort ye thither unto us; our God will fight for us." — Nehemiah 4:20 (ASV)

In what place therefore you hear the sound of the trumpet
Be it what part of the wall soever they were at work, even the most distant:

resort you there to us ;
to Nehemiah, and the half of his servants armed, where the trumpet was blown; that was to be the place of rendezvous:

our God shall fight for us ;
and give us victory over our enemies; none have any reason to be intimidated, when they shall hear the sound of the trumpet.