Genesis 33:13

And he said unto him, my lord knoweth the children [are]
tender
The eldest being but thirteen years of age, and the youngest about six; and Esau might easily perceive by their stature that they were young and tender, and not able to bear either riding or walking very fast: and the flocks and herds with young [are] with me;
or "upon me" ^F18; the charge of them was upon him, it was incumbent on him to take care of them, and especially in the circumstances in which they were, being big with young, both sheep and kine; or "suckling", giving milk to their young, as the Targums of Onkelos and Jonathan, and so having lambs and calves, some of them perhaps just yeaned and calved, they required more attendance and greater care in driving them, not being able to travel far in a day: and if men should overdrive them one day, all the flock will die;
if he, and the servants under him, should push them on too fast, beyond their strength, even but one day, all in the above circumstances would be in danger of being lost through overmuch fatigue and weariness.