John Calvin on Luke 1:56-57

The amount of this narrative is, that the birth of John was distinguished by various miracles, which gave reason to expect, that something great and remarkable would appear in the child himself at a future period. For the Lord determined to confer upon him from the womb remarkable tokens, that he might not afterwards come forward, as an obscure and unknown person, from the crowd, to discharge the office of a Prophet. First Luke relates, that Mary remained about three months with her cousin, — or, in other words, till the birth of the child: for it is probable that she had no other reason for staying so long, but to enjoy the exhibition of divine grace, which had been suggested to her by the angel for the confirmation of her faith.