There are two principles in this promise, which do for the most part regulate all the dealings of God.
I. The first part is a principle of surprise. God delights to frustrate expectations. He introduces His power in a manner and at a moment the least anticipated. The day seems just passing the darkness gathering everything looks for night when all in a moment the light kindles into more than meridian lustre. "At evening time it is light." Thus God keeps to Himself the sovereignty; man is humbled to the dust; reason is all put aside, and God's glory and God's love stand out all alone in the ascendant.
II. The second principle is that of patience. The blessing waits till the evening. It was not in hope's first beaming; it was not in the world's full glare; but in the quiet waiting-time it comes. When faith has been exercised, and graces have been tried, and the heart has been disciplined, do not doubt but that the morning's gifts, be they what they may, are as nothing to the evening's love. The sun may have been shining on you all the day through; still "at evening time it shall be light."
J. Vaughan, Fifty Sermons,2nd series, p. 187.
References: Zechariah 14:7. Spurgeon, Sermons,vol. iii., No. 160. Zechariah 14:8. Ibid., Morning by Morning,pp. 183, 278; J. Wells, Thursday Penny Pulpit,vol. v., p. 205.