Genesis 26:2

It had been in Izhak's heart to go down to Mizraim; but the Lord appeared to him, and said, Go not down to Mizraim; dwell in the land as I have told thee;

DWELL IN THE LAND WHICH I SHALL TELL THEE OF. It is incomprehensible that G-d should tell Isaac at one time, Dwell in the land which I shall tell thee of, [and in the following verse continue], Sojourn in this land, [and in both cases be referring to the same land]. Instead, its explanation is as follows: “Go not down into Egypt, and dwell all your days in the land which I shall tell you from time to time. At the bidding of G-d you should move, and at the bidding of G-d you should encamp, and right now, sojourn in this land, the land of the Philistines, for unto thee and unto thy seed I will give it, even as it is written, Counted to the Canaanites are the five lords of the Philistines.”
It is possible that [the event referred to in the beginning of the verse], And the Lord appeared unto him, and said … dwell in the land which I shall tell thee of, happened earlier so that before Isaac left his place it was said to him, “Go not down into Egypt; dwell in the land which I shall tell thee of when you will be there. Now dwell in this land, the land of Canaan, which will comprise many peoples and many lands, for I now command that you should not leave it forever for all these lands will I give to thy seed.” Following this command, Isaac journeyed from his place because of the famine to go into all the lands of Canaan, to dwell in the land which He would tell him. And when he came to Gerar, He said to him, “Dwell here.” It was not necessary however for Scripture to detail this for it is known that Isaac would not transgress the command of G-d., he left his place and went searching within the land of Canaan for a new home. When he finally reached Gerar he was told, Sojourn in this land. Thus Ramban explains that there was a lapse of [[illegible]] Verses 2 and 3. The original difficulty which Ramban mentions at the beginning of his comments on this verse is thus removed. A similar case of interpretation appears in the verse, Upon one of the mountains which I will tell thee of, as I mentioned there.

אל תרד מצרימה, do not let the shortage of grass to feed your livestock be the cause of moving to Egypt. (as the sons of Yaakov claimed in 47,4 to explain why they had moved to Egypt.)

שכון בארץ אשר אומר אליך, make huts for the shepherds and pens your livestock in the places which I will specify for you.

וירא, perhaps it had been part of Yitzchok’s plan to move all the way to Egypt as had done his father in similar circumstances, knowing that the food supply in Egypt was more abundant than that in any other country in the civilised world at the time. G’d appeared to him, meaning to dissuade him from carrying out such a plan, seeing that in the Land of the Philistines there was no famine at the time. In view of this, G’d said it would be better for him to reside there on a temporary basis than to move all the way south to Egypt. The Land of the Philistines is historically considered as part of the Land of Canaan as we have written in connection with 15,21 in reference to 15,18. G’d repeats this in verse 3 so that there could be no doubt about it [as some of us might have thought after considering that Avraham might have signed it away when he concluded his treaty with Avimelech at Beer Sheva. Ed.]

שכון בארץ אשר אמר אליך, in this verse the instruction is שכון, “make a permanent residence,” whereas in verse 3 the same instruction speaks of גור בארץ, “establish a temporary residence.” The commandment is reinforced that Yitzchok should not leave the Land of Canaan at that time or at any time in the future, the reason being

אשר אומר אליך, what I have said to your father is equally valid for you.