On the altar you are looking at the same thing as you saw there last night. You have not heard, however, what this is, what it signifies, or about the greatness of the reality of which it is a sacrament. Your eyes are looking at bread and cup. This is the evidence before your physical sight. But your faith must be instructed concerning it- this bread being Christ 's Body and the cup containing His Blood. Though perhaps these words may be enough to initiate faith, faith must be further instructed in accordance with the Prophet's words: 'Believe that you may understand'
Saint AugustineI count myself one of the number of those who write as they learn and learn as they write.
Saint AugustineThe bread that you see on the altar is the Body of Christ as soon as it is sanctified by God's word. The chalice, or better what is contained in the chalice, is the Blood of Christ as soon as it is sanctified by God's word
Saint AugustineAs to those other things which we hold on the authority, not of Scripture, but of tradition, and which are observed throughout the whole world, it may be understood that they are held as approved and instituted either by the apostles themselves, or by plenary Councils, whose authority in the Church is most useful, e.g. the annual commemoration, by special solemnities, of the Lord's passion, resurrection, and ascension, and of the descent of the Holy Spirit from heaven, and whatever else is in like manner observed by the whole Church wherever it has been established.
Saint Augustine