If a fireman has to go to work, he has to dress accordingly. When a mountain rescuer goes up the mountains on a rescue mission he puts on his appropriate clothes. If a surgeon is about to perform a surgery, he dresses accordingly. The diver, who is attempting to study the bottom of the sea, must put on his special suit.
In a similar way, when a child believes in the Lord Jesus, he must be equipped properly, so that he might be safe when spiritual attacks come his way.