Commentaire sur La Genèse 37:34

ימים רבים MANY DAYS — twenty-two years (Genesis Rabbah 84:20) — from the time he left him until Jacob went down to Egypt. For it is said, (v. 2) “Joseph was seventeen years old” (when all these events happened), and he was thirty years old when he stood before Pharaoh; seven years of plenty and two years of famine had passed by the time Jacob came to Egypt — making in all 22 years. These correspond to the 22 years during which Jacob had not practised the duty of honouring his parents (that is, the period during which he did not reside with them and attend to their needs) (Megillah 17a): viz., the twenty years he stayed in Laban’s house and the two years on the journey when he was returning from Laban’s house — one and a half year at Succoth and six months at Bethel. This is what he meant when he said to Laban (31:41) “These twenty years that I have been in thy house are לי” — they are for me — the responsibility for them lies upon me (לי being taken as עלי) and at sometimes I shall be punished for a period equal to them.

וישם שק במתניו, a section of fabric which sacks are made of. He draped his loins in enough of this material to demonstrate his being in mourning.

ויקרע יעקב, he mourned him excessively because he had loved him so inordinately. Besides, he blamed himself partially for his fate for having sent him on what turned out to have been a dangerous mission.