Genesis 37:4

And when his brethren saw that their father loved him more than all his brethren, they hated him, and could not speak peaceably unto him. They believed that Jacob's preference for Joseph indicated that the right of the first-born was to be conferred upon him. As a result, their envy and hatred grew to the point that they were no longer able to greet him kindly nor to talk with him frankly and peaceably. Envy very often grows into hatred and results in manifold sins.