Genesis 13:7

And there was strife between the herdsmen.

The servants of each chieftain, zealous for their master's interest, would seek the supplies of water and the best pastures, for the cattle of which they had charge. Conflicting interests would produce collisions, and they came to blows.

And the Canaanite and Perizzite were then in the land.

This statement is made in order that the danger which strife would cause may be apparent. It was needful that the two kinsmen be united and strong, lest they should be attacked by the half-savage inhabitants. The dwellers of the country, in that age, were not numerous, and under ordinary circumstances would not dare to molest such powerful chieftains as Abraham and Lot.