John Calvin Commentary Genesis 26:2

"And Jehovah appeared unto him, and said, Go not down into Egypt. Dwell in the land which I shall tell thee of." — Genesis 26:2 (ASV)

And the Lord appeared to him. I do not doubt that a reason is given here why Isaac went to the country of Gerar rather than to Egypt, which perhaps would have been more convenient for him; but Moses teaches that he was restrained by a heavenly oracle, so that he was not left with a free choice.

It may be asked here, why did the Lord prohibit Isaac from going to Egypt, where He had allowed his father to go? Although Moses does not give the reason, we may conjecture that the journey would have been more dangerous for the son. The Lord could indeed have also endowed the son with the power of His Spirit, as He had done his father Abraham, so that the abundance and delicacies of Egypt would not have corrupted him by their allurements. But since He governs His faithful people with such moderation that He does not correct all their faults at once and make them entirely pure, He assists their weaknesses and anticipates, with suitable remedies, those evils by which they might be ensnared.

Therefore, because He knew that there was more weakness in Isaac than there had been in Abraham, He was unwilling to expose him to danger; for he is faithful, and will not suffer his own people to be tempted beyond what they are able to bear (1 Corinthians 10:13). Now, just as we must be persuaded that however arduous and burdensome the temptations that come upon us may be, Divine help will never fail to renew our strength, so, on the other hand, we must beware that we do not rashly rush into dangers; but each person should be admonished by his own weakness to proceed cautiously and with fear.

Dwell in the land. God commands him to settle in the promised land, yet with the understanding that he should live there as a stranger. The indication was thus given that the time had not yet arrived when he would exercise dominion over it. God indeed sustains his mind with the hope of the promised inheritance but requires this honor to be given to His word: that Isaac should remain inwardly at rest amidst outward disturbances. And truly, we never lean on a better support than when, disregarding the appearance of present things, we depend entirely on the word of the Lord and apprehend by faith that blessing which is not yet apparent.

Moreover, He again impresses the promise previously made, in order to make Isaac more ready to obey. For the Lord is accustomed to awaken His servants from their laziness in this way, so that they may fight valiantly for Him, while He constantly affirms that their labor shall not be in vain. For although He requires from us a free and unreserved obedience, as a father does from his children, He yet so condescends to the weakness of our capacity that He invites and encourages us by the prospect of reward.