Sforno on Exodus 13:19/ספורנו על שמות י״ג:י״ט

1ויקח משה את עצמות יוסף עמו, seeing that he was now the leader of the nation it was up to him to make good on the oath Joseph

2השבע השביע את בני ישראל, any obligation undertaken communally must be honoured by the leader of that community when the time and opportunity presents itself to discharge that obligation.