Ibn Ezra on the Torah

“Lech Lecha (Go forth)” - God already commanded Abraham, when they were still in Ur Kasdim, to leave his land and country and birthplace and the house of his father. And the reason is that God knew that Terach, after he went to go to the Land of Canaan, would stay in Haran. And Terach did not die until 60 years after Abraham left his house in Haran. But the Torah did not detail all the years after he left Ur Kasdim. And after it says, “that I will show you,” He revealed to him the secret. That’s why it says, in Chapter 11, “They went out to go to the Land of Canaan. Or, the reason it says "I will show you" is that He is saying, "All the land that you can see, I will give you."

The Canaanites were then in the land: Perhaps the Canaanites captured the land of Canaan immediately thereafter (cf. Rashi ad loc). But if it is not so, then there is a secret to the matter, and whoever discerns it should be silent (i.e. keep it secret).