Genesis 26:2 - Joseph Benson’s Commentary on the Old and New Testaments

Go not down into Egypt Whither, it is likely, Isaac had intended to go, it being a very fruitful country, and he being encouraged to go thither by his father's example, on a similar occasion. No doubt God had wise reasons for prohibiting his going; but as he has not been pleased to acquaint us with them, to spend time in conjecturing what they were, would be giving ourselves trouble to no purpose.