Luke 1:7

And they had no child The providence of God so ordering it, that the birth of John the Baptist might be the more remarkable, and might excite the greater attention; because that Elisabeth was barren Even when in the flower of her age. And they both were now well stricken in years Here, then, was a double obstacle in the way of their having children, both the natural barrenness of Elisabeth, and the old age of them both; and, consequently, a double proof of the supernatural agency of God in the birth of John, evidently showing him to be a person miraculously sent by God. It is worthy of observation here, that many eminent persons under the patriarchal and Mosaic dispensations, were born of mothers that had been long barren, as Isaac, Jacob, Joseph, Samson, Samuel, and here John the Baptist, to render their birth the more extraordinary, and the blessing of it the more valuable in the eyes of their parents; and to show, that when God keeps his people waiting long for a particular mercy, he is sometimes pleased to recompense them for their patience, by doubling the worth of it when it is given.