Genesis 29:8

And they said, we cannot
That is, water the sheep; either because the stone was a great one, as Jarchi observes, and therefore used to be removed by the joint strength of all the shepherds when they came together, though Jacob rolled it away of himself afterwards; but this is imputed to his great strength: or rather it was a custom that obtained among them, or an agreement made between them, that the stone should not be removed from the mouth of the well, and any flock watered,

until all the flocks be gathered together;
and therefore they could not fairly and rightly do it, without violating the law and custom among them:

and [till] they roll the stone from the well's mouth;
that is, the shepherds of the several flocks:

then we water the sheep;
and not till then.