The sermon with central theme Diliges Dominum Deum was preached by Jan Hus as his first synodical sermon at the synod of Prague Archdiocese on the feast of st. Lucas at the 19th of October 1405. This text, written in form of thematic preaching, is concerned with usual problems of the Church at that time, especially with sins of adultery and simony. The value of the sermon lies in an opening part, in which Jan Hus described his ecclesiological meanings based on the opinions of John Wycliff. This occurence of Wycliffe's ecclesiology is one of the earliest evidences of his influence over Jan Hus' concept of the Church. The aim of this paper is to introduce the sermon Diliges and the context, in which was preached. Attention will be paid not only to content, but also to form of the sermon.