Don't Go Back There are several reasons why it would not have been wise for Isaac to venture back to his ancestor's homeland:
1. As Leslie had pointed out, there would have been a strong temptation for Isaac to stay because of the insistence of Rebecca's relatives. (Genesis 24:55-58) Just being around kinfolk would have been a strong draw to prevent Isaac from going back to the Promised Land which God had given to Abraham through covenant---which eventually had redemptive purposes for all mankind! In thy Seed shall all the nations be blessed.
2. There was also the danger of Isaac resorting back to worshipping the idolatrous, false gods of that region of Mesopotamia. Abraham's blessing was intricately tied in to the worship of Jehovah God, creator of heaven and earth. The relatives of Abraham in Haran still worshiped idols. All would have been lost if Isaac succumbed to idolatry. (Genesis 12:8, 31:19,32 father's idols)
3. Notice that the land up north amongst the rivers of Mesopotamia were more like paradise in comparison to the rocky mountains of southern Israel, and the Negev. The lure of the pleasant landscape would have been attractive to Isaac as a place to raise a family. Going from water hole to water hole in the south, trying to raise goats and sheep on scraggy brush would not have been as desirable. (Famine prone Genesis 12:10; 41:57)
4, The land of Abraham's sojourn was populated with strangers to Abraham's clan. Some were outright bandits. (Genesis 15:19-21, Kenites, Kenizzites, Kadmonites, Hittites, Perizzites, Rephaims, Amorites, Canaanites Girgashites, Jebusites; 37:1) At times there was conflict with them, and only Abraham's strategy saved the day. But in Haran, Isaac would have been surrounded with kinfolk he could relate to, so he might have been tempted to rest his bones up there, and not return to the "Promised Land," frustrating God's plans.
5, And lastly, Abraham knew what his devious kinfolk were like! Isaac would have been taken advantage of by their chicanery---as is evidenced by the future run in that Jacob had with Laban. The personality (spiritual DNA) of the clan was not that sanctified. Abraham didn't want Isaac to pick up on those habits. (Jacob later exhibited such bad character (through heredity?). (Genesis 31:7, deceived me... ten times; 31:32 stolen; 27:12; deceiver? And his mother said, Upon me by thy curse 27:13)
Sufficient were the several reasons why Abraham had the insight and wisdom to instruct his Servant not to allow Isaac to return to Haran. But the New Testament provides insight and puts this question into perspective in Hebrews' "Faith chapter":
By faith Abraham, when he was called to go out into a place which he should after receive for an inheritance, obeyed; and he went out, not knowing whither went. By faith he sojourned in the land promise, as in a strong country, dwelling in tents with Isaac and Jacob,the heirs with him of the same promise; for he looked for a city which hath foundations, whose builder and maker is God...
And truly, if they had been mindful of that country from whence they came out, they might have had opportunity to have returned. But now they desire a better country, thetis, a heavenly; wherefore God is not ashamed to be called their God, for He has prepared for them a city! (Hebrews 11:8-10, 15-16)
If Isaac ventured back up to the country from whence Abraham came he would have seen all the homes of brick and mortar, all the walled villages protected from invaders, the snug cottages with gardens...and all these were much more secure and comfortable than the tents he was living in. Tents he had to pitch up and then tear down as a wandering nomad. Tent living subject to the oppressive siroccos, the cold nights, and the threat of bandits. And all the wandering like a sojourner in a strange land.
The temptation would have been too great to not stay in Canaan. And he would have lost out on the great Promise God had made for him and his future descendants. The promises to Abraham would have been nullified.
But Abraham knew the awesome blessing and favor God had given him, and he wasn't about to let anything stand in its way...according to the scriptures in Hebrews 11! Isaac therefore must not return back north to the country they had come from.
And this what the walk of faith in life is all about. 1 Corinthians 5:7: We walk by faith, not by sight.