Abraham stood over them under the tree and they ate.—Genesis 18:8
When Abraham stood over them, only then were the angels capable of eating and elevating their food.—Rabbi Dov Ber of Lubavitch

What more spiritual activity could there be than eating, when it is done not only with the mouth, but with the mind?

When a human being eats and his mind and soul are engaged, he separates the good from the bad, the divine from the mundane. The food rises to a higher realm. And then the divine sparks he has discovered within the food carry him yet higher.

The angels are incapable of such a feat—unless a human soul provides them the power. For, in mindful eating, the human soul reaches beyond the entire order of being.

As the Creator formed from the spiritual the physical, so the human being transforms the physical into spiritual.

Maamar, Vayeira, 5738 (1977)