John Calvin Commentary Genesis 40:5

"And they dreamed a dream both of them, each man his dream, in one night, each man according to the interpretation of his dream, the butler and the baker of the king of Egypt, who were bound in the prison." — Genesis 40:5 (ASV)

And they dreamed a dream. What I have previously alluded to regarding dreams must be recalled to memory: namely, that many frivolous things are presented to us, which pass away and are forgotten; some, however, have the force and significance of prophecy. These two dreams were of this kind, by which God made known the hidden result of a future matter.

For unless the mark of a heavenly oracle had been engraved upon them, the butler and the baker would not have been in such consternation of mind. I acknowledge, indeed, that people are sometimes vehemently agitated by vain and rashly conceived dreams, yet their terror and anxiety gradually subside; but God had fixed an arrow in the minds of the butler and the baker, which would not allow them to rest; and by this means, each was made more attentive to the interpretation of his dream. Moses, therefore, expressly declares that it was a presage of something certain.