Then over Mount Zion and over all who are gathered there, the Lord will send a cloud in the daytime and smoke and a bright flame at night. God's glory will cover and protect the whole city. 1
References for Isaiah 4:5
4.5 Ex 13.21; 24.16.
His glory will shade the city from the heat of the day and make it a place of safety, sheltered from the rain and storm.