4th Century
St. Ambrose of Milan
Patristic Period
St. Ambrose of Milan (c. 339 – 397), Bishop of Milan and Doctor of the Church. Wikipedia
"Before it is consecrated, it is bread, but when the words of Christ have been added, it is the body of Christ. Therefore hear him saying: Take and eat ye all of it; for this is my body. And before the words of Christ it is a cup full of wine and water. When the words of Christ have operated, then and there it is made to be the blood of Christ which redeemed the people. "
On the Sacraments
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Why this quote matters
Western patristic witness to consecration by Christ's words.
Source citation: On the Sacraments, Book IV.