He's discussing the 19th chapter of John's Gospel. Isn't that what was requested?
If one closes one's eyes to 2,000 years of Church teaching and tradition, if one pretends it doesn't exist, then one can quite happily pick up a Bible and draw any number of conclusions about what Scripture says or doesn't say. That's the whole problem.
It's difficult to get this point across to disciples of modern American congregationalism, completely adrift as it is, on a sea of individualism and subjectivism. It has severed all connections with the Church's Apostolic roots and is largely reliant on personal, circumstantial and arbitrary reading of Scripture. I think we're familiar with the argument that those who followed in the footsteps of the Apostles in the early centuries of the Church, didn't really get it and it's only in the latter days that we've finally come to understand the Gospel. That's dangerous thinking.
To scorn the words of Doctors of the Church such as Augustine, Athanasius and Jerome, is unwise in the extreme.
The quote from him was from his commentary on the Book of Matthew. The Church fathers all based their beliefs on the perpetual Virginity of Mary on the Bible. They were scholars and would discuss, debate and teach the faith and show how the Church’s teachings were supported by Scripture. If their discussion was on matters which were not yet official dogma they would lay out their arguments based on Scripture.
This was done not only regarding the Perpetual Virginity of Mary but such universally accepted doctrines which were once questioned such as the Divinity of Christ.