Matthew Poole and continuators on Genesis 41:2

2 And behold, there came up out of the river , seven well-favoured kine , and fat-fleshed, and they fed in a medow.

This suits well with the nature of the thing, for both the fruitfulness and the barrenness of Egypt depended under God upon the increase or diminution of the waters of that River.

Which when they appeared in dreams did portend, in the opinion of the learned Egyptians, the years or times to come, and them either good or bad according to their quality.