John Calvin Commentary Luke 1:58

"And her neighbors and her kinsfolk heard that the Lord had magnified his mercy towards her; and they rejoiced with her." — Luke 1:58 (ASV)

And her neighbors and relatives heard. It may be doubted whether these people perceived the wonderful kindness of God solely from the fact of her being blessed with a child, or whether they had previously heard that an angel had appeared to Zacharias and promised him a son. This was certainly no ordinary divine favor, that, contrary to the course of nature, a barren woman at a very advanced age had brought forth a child. It is possible that, for this reason alone, they magnified the divine goodness.

On the eighth day, from a sense of duty or from courtesy, as is customary on such occasions, some people assembled; but God used this occasion to make them witnesses and spectators of his power and glory. There can be no doubt that the extraordinary birth brought a greater crowd. They had considered it a prodigy to see an old and barren woman suddenly become pregnant; and now that the child was born, their astonishment was renewed and increased.

We infer from the words of Luke that, though they circumcised their children at home, they were not accustomed to do so without gathering a numerous assembly; and with good reason, for it was a common sacrament of the church, and it was not proper to administer it secretly or privately.