John Gill Commentary Mark 12:26

"But as touching the dead, that they are raised; have ye not read in the book of Moses, in [the place concerning] the Bush, how God spake unto him, saying, I [am] the God of Abraham, and the God of Isaac, and the God of Jacob?" — Mark 12:26 (ASV)

And as touching the dead, that they rise
For the proof of the doctrine of the resurrection of the dead,

have you not read in the book of Moses ;
that is, in the law of Moses; for though it was divided into five parts, it was but one book; just as the Psalms are called the Book of Psalms, (Acts 1:20) , and the Prophets, the Book of the Prophets, (Acts 7:42) . The book of Exodus is particularly intended; for the passage referred to is in (Exodus 3:6) ,

how in the bush God spoke to him ,
or "out of the bush", as the Syriac and Persic versions read;

saying, I am the God of Abraham, and the God of Isaac, and the God
of Jacob? (See Gill on Matthew 22:31), (See Gill on Matthew 22:32).