A close look at the whole history of salvation reveals that mercy is precisely the common thread of salvation, because it is the main divine attribute. Therefore, it is a central theme for the Christian faith. From the theological point of view, its right understanding has an enormous relevance for the pastoral and spiritual life of the missionary disciples of Jesus Christ. Our focus on this theme is based on the Aponius work, which presents a peculiarity in relation to other comments about the biblical book of the Song of Songs. In fact, more than emphasizing the spousal covenant between God and humanity, in the web of love between the spouses of the biblical poem, Aponius sees a prefiguration of the history of salvation. As a very unknown author, our first part of the research focuses mainly on the Aponius person and his work. Similarly, we also focus on the influence that his Commentary had on some later authors. Then, we turn to the hermeneutics of the Song of Songs, considering the way in which this biblical book was interpreted both by Jewish tradition and by the Fathers of the Church. The purpose of this part is to reveal the characteristics of Aponius exegesis, in which our author inserts his doctrinal and spiritual expositions. Finally, our thesis focuses on the chosen theme, starting from the Trinity as a source of mercy and emphasizing the action of the merciful Christ-Spouse, who, in the Pascal mystery, marries the Church forever, making it a sacrament of mercy. As a member of the Bride Church, each Christian is called to experience this nuptial mystery in himself and to be a witness of divine mercy.