Exodus 12:34

טרם יחמץ BEFORE IT WAS LEAVENED — The Egyptians would not allow them to stay long enough for the dough to become leavened. משארתם (from the root שאר “to be left over”) denotes the leavings (what was left) of the unleavened bread and bitter herbs (Mekhilta). על שכמם UPON THEIR SHOULDER — Although they took many cattle with them yet they bore this upon their shoulders because the commands of God were so dear unto them (Mekhilta).

וַיִּשָּׂ֥א הָעָ֛ם אֶת־בְּצֵק֖וֹ טֶ֣רֶם יֶחְמָ֑ץ מִשְׁאֲרֹתָ֛ם צְרֻרֹ֥ת בְּשִׂמְלֹתָ֖ם עַל־שִׁכְמָֽם׃

And the people took their dough before it was leavened, their kneading troughs being bound up in their clothes upon their shoulders.