פירוש על בראשית 37:4

ולא יכלו דברו לשלום AND THEY COULD NOT SPEAK PEACEABLY TO HIM — from what is stated to their discredit we may infer something to their credit: they did not speak one thing with their mouth having another thing quite different in their hearts (Genesis Rabbah 84:9).

ויראו אחיו כי אותו אהב אביהם, here Yaakov had committed an error, allowing the love in his heart for Joseph to be now become visible through preferential treatment of him.

ולא יכלו דברו לשלום, any conversation with Joseph did not revolve around peacefully discussed matters of common interest, but concerned only matters of dispute between them.