“Brothers, the Scripture had to be fulfilled that the Holy Spirit foretold through the mouth of David concerning Judas, who became a guide for those who arrested Jesus.
16. It was meet that the Scripture should be fulfilled. Because Peter doth speak in this their assembly, therefore the Papists will have him to be the head of the church. “Universae Ecclesiae,” the Universal Church. As though no man might speak in any assembly of the godly but he should straightway be Pope.
The sin of Judas was not only his shame and ruin, but it made a vacancy in the college of the apostles. They were ordained twelve, with an eye to the twelve tribes of Israel, descended from the twelve patriarchs; they were the twelve stars that make up the church's crown (Rev 12:1), and for them twelve thrones were designated, Mat 19:28.
Commenting on Acts 1:15-26
Men and brethren,.... Which is said not so much by Peter to express his modesty, and humility, and his brotherly love; or on account of the spiritual relation that subsisted between him and the persons he speaks to, as it was a common form used in addresses; see Act 7:2 it should seem, that the women, were not reckoned into the number of the hundred...