The influence of St. Augustine on the development of western latin theological thinking is significant. In many ways, he also influenced thinking of counter-reformation and reformation theologians, mainly Martin Luther. Martin Luther quotes the passage of the 80th homily on the Gospel of John in the third paragraph of the Smalcald Articles. Therefore, it is certain that Augustine influenced the understanding of baptism, mainly the relation between faith and word during administration of the sacrament of baptism. The aim of our study is to offer theological analysis of the 80th homily on the Gospel of John mentioned above in the context of Augustine´s thinking. It is a short dictated text written by the theologian of Hippo in 419-423 where he explains the Gospel of John 15, 1-5 word by word. Reformation, counter-reformation and post-Trentian theologians used to refer to the third paragraph of the 80th homily too often and their interpretation was influenced by their position, whether they were on the side of Catholics or Protestants. It is interesting that although the text was often quoted, there were only several studies that dealt with it in a professional way. Augustine´s homily reflects the spiritual wealth of the battle with donatism (the role of administrator and recipient of the sacrament of baptism) and pelagianism (baptism of children). In this study, we point to the fact that it is a commentary on the Sacred Scripture, therefore we analyse the homily as a whole. The study also includes the first complete translation of the homily into Slovak language.