John Gill Commentary Judges 18:10

"When ye go, ye shall come unto a people secure, and the land is large; for God hath given it into your hand, a place where there is no want of anything that is in the earth." — Judges 18:10 (ASV)

When you go, you shall come to a people secure, and to a large
land
For though it was but one city, its territories were large, and the villages belonging to it might be many. These factors, combined with the security of the people (who were not upon their guard and could easily be surprised and taken), are the arguments used by the spies to encourage their countrymen to go up and take it. To these, they add others:

for God has given it into your hands ;
They concluded this from the state and condition they found the people in, who were thoughtless and defenceless. Alternatively, it may be on account of the oracle in Micah's house they had consulted, and to which they gave credit. Though some think their faith was grounded upon this place being given by lot to the tribe of Dan, this does not appear:

a place where there is no want of anything that is in the earth ;
in the land of Canaan; meaning, that there was nothing in the whole land but might be found there, as wheat and barley, vines, fig trees, pomegranates, olives, and honey, with all other necessaries and conveniences of life.