Or HaChaim on Exodus 6:8/אור החיים על שמות ו׳:ח׳

1 והבאתי אתכם אל הארץ, "And I shall bring you to the land, etc." It is difficult to reconcile this promise with our tradition that G'd speaks the unvarnished truth when we know it to be a fact that the generation G'd was addressing at that time did not get to the Holy Land. Only the children of that generation actually crossed the Jordan and took possession of the land of Canaan. Every one of the people who left Egypt at an age of twenty or over died on the way. Our problem is even more serious in view of the statement of our sages (Shemot Rabbah 6:4) that the word לכן in 6,6, is a form of an oath.

2I believe that G'd Himself was already aware of this problem and that is why He prefaced the statement "I will bring you to the land, etc," with the words: "you will know that I am the merciful G'd who is about to take you out from under the slave labour of Egypt." The two statements are to be considered as conditions. What G'd meant was simply this. "Provided that you will have realised that I am the One who takes you out of Egypt and that I have demonstrated to be the merciful G'd,-then you will also experience that I shall bring you to the land which I have sworn to your forefathers and will give it to you as an inheritance." G'd was very careful to insert this condition in the very midst of the promise He made and not only as an afterthought. In the event that the Israelites would not fulfil the conditions laid down history would have to take its course in accordance with their conduct.