Jamieson, Fausset and Brown on Genesis 37:4

4. could not speak peaceably unto him--did not say "peace be to thee" [Ge 43:23, &c.], the usual expression of good wishes among friends and acquaintances. It is deemed a sacred duty to give all this form of salutation; and the withholding of it is an unmistakable sign of dislike or secret hostility. The habitual refusal of Joseph's brethren, therefore, to meet him with "the salaam," showed how ill-disposed they were towards him. It is very natural in parents to love the youngest, and feel partial to those who excel in talents or amiableness. But in a family constituted as Jacob's--many children by different mothers--he showed great and criminal indiscretion.