John Gill Commentary Exodus 23:31

"And I will set thy border from the Red Sea even unto the sea of the Philistines, and from the wilderness unto the River: for I will deliver the inhabitants of the land into your hand: and thou shalt drive them out before thee." — Exodus 23:31 (ASV)

And I will set your bounds
The bounds of the land of Canaan, which in process of time it should reach unto, though not at once, not until the times of David and Solomon, (2 Samuel 8:1–18) (1 Kings 4:24) which bounds were as follow:

from the Red sea even unto the sea of the Philistines :
the Red sea was the boundary eastward, as the sea of the Philistines, or the Mediterranean sea, was the boundary westward:

and from the desert unto the river ;
the desert of Shur or Arabia, towards Egypt, was the boundary southward, as the river Euphrates was the boundary northward, and is the river here meant, as the Targum of Jonathan expresses it; and so Jarchi interprets it, and generally others:

for I will deliver the inhabitants of the land into your hand ;
the greater part upon their entrance into it, and settlement in it, and the rest afterwards:

and you shall drive them out before you ;
not all at once, but by degrees, as before observed.