When Terah was older he left Ur of the Chaldeans with Abram, Sarai and Lot. This was during the final part of Terah’s life because Abram was born when he was 130 years or older. Abram was also already married to Sarai when they left Ur.
How is it possible that we read here that they left Ur for Canaan under the leadership of Terah? After all, the Lord had called Abram and not Terah? God had indeed already called Abram in Ur, in Mesopotamia. We also read this very clearly in Acts 7:2–4.
It is important to keep in mind here that Terah was the head of the family. Even if he leaves with Abram (as God specifically called Abram) he is still the head of the family. When we read in Genesis 11:31 that they set out on a journey “to go into the land of Canaan” it does not necessarily mean that Terah and Abram already knew at the time that the land God would designate for them would be Canaan. By the time this was written down, the author used the name Canaan because he knew (in retrospect) that this was the land the Lord had in mind.
31 Terah took Abram his son and Lot the son of Haran, his grandson, and Sarai his daughter-in-law, his son Abram’s wife, and they went forth together from Ur of the Chaldeans to go into the land of Canaan, but when they came to Haran, they settled there.