Numbers 22:21-23 NIV
Balaam got up in the morning, saddled his donkey and went with the
princes of Moab. But God was very angry when he went, and the angel
of the LORD stood in the road to oppose him. Balaam was riding on
his donkey, and his two servants were with him.
When the donkey
saw the angel of the LORD standing in the road with a drawn sword
in his hand, she turned off the road into a field.
Balaam beat her to get her back on the road.
Numbers 22:31 NIV
Then the LORD
opened Balaam's eyes, and he saw the angel of the
LORD standing in the road with his sword drawn. So he bowed low and
fell facedown.
The donkey can see the angel without God having to open its
eyes.