Charles Ellicott Commentary Numbers 34:6

"And for the western border, ye shall have the great sea and the border [thereof]: this shall be your west border." — Numbers 34:6 (ASV)

And as for the western border ... — Better, And as for the western border, you shall have the great sea and (its) border (i.e., its coast). (See Joshua 15:47, the great sea and the border thereof.)