15 Lastly, when both these things have been briefly touched, afterwards he is evidently following out the order of the narrative. “Because they believed not in God, nor hoped in His saving health”. For when he had told why fire was lighted in Jacob, and anger went up upon Israel, that is to say, “because they believed not in God, nor hoped in His saving health:” immediately subjoining the evident blessings for which they were ungrateful, he says, “and He commanded the clouds above, and opened the doors of Heaven”.
“And He rained upon them manna to eat, and gave them bread of Heaven”. “Bread of angels man did eat: dainties He sent them in abundance”. He brought over the South Wind from Heaven, and in His virtue He led in the South West Wind. “And He rained upon them fleshes like dust, and winged fowls like the sand of the sea”. “And they fell in the midst of their camp, around their tabernacles”. “And they ate and were filled exceedingly; and their desire He brought to them: they were not deprived of their desire”.
Behold why He had delayed. But what He had delayed let us hear. “Yet the morsel was in their mouths, and the anger of God came down upon them”. Behold what He had delayed. For before “He delayed:” and afterwards, “fire was lighted in Jacob and anger went up upon Israel.” He had delayed therefore in order that He might first do what they had believed that He could not do, and then might bring upon them what they deserved to suffer. For if they placed their hope in God, not only would their desires of the flesh but also those of the spirit have been fulfilled.
For he that...“opened the doors of Heaven, and rained upon them manna to eat,” that He might fill the unbelieving, is not without power to give to believers Himself the true Bread from Heaven, which the manna did signify: which is indeed the food of Angels, whom being incorruptible the Word of God does incorruptibly feed: the which in order that man might eat, He became flesh, and dwelled in us. For Himself the Bread by means of the Evangelical clouds is being rained over the whole world, and, the hearts of preachers like heavenly doors, being opened, is being preached not to a murmuring and tempting synagogue, but to a Church believing and putting hope in Him.
He is able also to feed the feeble faith of such as tempt not, but believe, with the signs of words uttered by the flesh and speeding through the air, as though it were fowls: not however with such as come from the north, where cold and mist do prevail, that is to say, eloquence which is pleasing to this world, but by bringing over the South Wind from Heaven; whither, except to the earth? In order that they who are feeble in faith, by hearing things earthly may be nourished up to receive things heavenly....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)