Hahn begins by describing the first mass he ever attended.
"There I stood, a man incognito, a Protestant minister in plainclothes, slipping into the back of a Catholic chapel in Milwaukee to witness my first Mass. Curiosity had driven me there, and I still didn't feel sure that it was healthy curiosity. Studying the writings of the earliest Christians, I'd found countless references to "the liturgy," "the Eucharist," "the sacrifice." For those first Christians, the Bible - the book I loved above all - was incomprehensible apart from the event that today's Catholics called "the Mass."
"I wanted to understand the early Christians; yet I'd had no experience of liturgy. So I persuaded myself to go and see, as a sort of academic exercise, but vowing all along that I would neither kneel nor take part in idolatry."
I took my seat in the shadows, in a pew at the very back of that basement chapel. Before me were a goodly number of worshipers, men and women of all ages. Their genuflections impressed me, as did their apparent concentration in prayer. Then a bell rang, and they all stood as the priest emerged from a door beside the altar.
Unsure of myself, I remained seated. For years, as an evangelical Calvinist, I'd been trained to believe that the Mass was the ultimate sacrilege a human could commit. The Mass, I had been taught, was a ritual that purported to "resacrifice Jesus Christ." So I would remain an observer. I would stay seated, with my Bible open beside me.
As the Mass moved on, however, something hit me. My Bible wasn't just beside me. It was before me - in the words of the Mass! One line was from Isaiah, another from Psalms, another from Paul. The experience was overwhelming. I wanted to stop everything and shout, "Hey, can I explain what's happening from Scripture? This is great!" Still, I maintained my observer status. I remained on the sidelines until I heard the priest pronounce the words of consecration: "This is My body . . . This is the cup of My blood."
Then I felt all my doubt drain away. As I saw the priest raise that white host, I felt a prayer surge from my heart in a whisper: "My Lord and my God. That's really you!"
I was what you might call a basket case from that point. I couldn't imagine a greater excitement than what those words had worked upon me. Yet the experience was intensified just a moment later, when I heard the congregation recite: "Lamb of God . . . Lamb of God . . . Lamb of God," and the priest respond, "This is the Lamb of God . . ." as he raised the host. In less than a minute, the phrase "Lamb of God" had rung out four times. From long years of studying the Bible, I immediately knew where I was. I was in the Book of Revelation, where Jesus is called the Lamb no less than twenty-eight times in twenty-two chapters. I was at the marriage feast that John describes at the end of that very last book of the Bible. I was before the throne of heaven, where Jesus is hailed forever as the Lamb. I wasn't ready for this, though - I was at Mass!
Hahn also has a brief online course of The Lamb's Supper: The Bible and the Mass. Perhaps it might be of value to inquiring minds. :)