Because There Was No Sun...
"Let the earth bring forth grass..." Hitherto the earth was naked and barren, now the Lord fructifies it by his word. For though it was already destined to bring forth fruit, yet till new virtue proceeded from the mouth of God, it must remain dry and empty. For neither was it naturally fit to produce anything, nor had it a germinating principle from any other source, till the mouth of the Lord was opened. For what David declares concerning the heavens, ought also to be extended to the earth; that it was
‘made by the word of the Lord, and was adorned and furnished by the breath of his mouth,’ (Psalm 33:6.)
Moreover, it did not happen fortuitously, that herbs and trees were created before the sun and moon. We now see, indeed, that the earth is quickened by the sun to cause it to bring forth its fruits; nor was God ignorant of this law of nature, which he has since ordained: but in order that we might learn to refer all things to him he did not then make use of the sun or moon.66 He permits us to perceive the efficacy which he infuses into them, so far as he uses their instrumentality; but because we are wont to regard as part of their nature properties which they derive elsewhere, it was necessary that the vigor which they now seem to impart to the earth should be manifest before they were created. We acknowledge, it is true, in words, that the First Cause is self-sufficient, and that intermediate and secondary causes have only what they borrow from this First Cause; but, in reality, we picture God to ourselves as poor or imperfect, unless he is assisted by second causes. How few, indeed, are there who ascend higher than the sun when they treat of the fecundity of the earth? What therefore we declare God to have done designedly, was indispensably necessary; that we may learn from the order of the creation itself, that God acts through the creatures, not as if he needed external help, but because it was his pleasure. When he says, ‘Let the earth bring forth the herb which may produce seed, the tree whose seed is in itself,’ he signifies not only that herbs and trees were then created, but that, at the same time, both were endued with the power of propagation, in order that their several species might be perpetuated. Since, therefore, we daily see the earth pouring forth to us such riches from its lap, since we see the herbs producing seed, and this seed received and cherished in the bosom of the earth till it springs forth, and since we see trees shooting from other trees; all this flows from the same Word. If therefore we inquire, how it happens that the earth is fruitful, that the germ is produced from the seed, that fruits come to maturity, and their various kinds are annually reproduced; no other cause will be found, but that God has once spoken, that is, has issued his eternal decree; and that the earth, and all things proceeding from it, yield obedience to the command of God, which they always hear.1John Calvin Commentary on the First Book of Moses Called Genesis (vol.1) (Grand Rapids: www.ccel.org)