Rashi on Genesis 37:4/רש"י על בראשית ל״ז:ד׳

1ולא 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).

2דברו means TO SPEAK TO HIM.