The person of the powerful Bishop of Krakow has always been of interest to historians. He attracted their attention not only as a statesman, but also as a prince of the Church. In addition to his well-known political involvement on a large scale, Zbigniew Oleśnicki led and managed a huge diocese on a daily basis. He also took decisions closely related to matters of worship, which are always of fundamental importance for the Church. This dimension of Zbigniew Olesnicki's activity is little known, which is why we would like to stop here and present the results of our research in this study. The main sources of information on this subject are the decisions of two Krakow Synods, collected in about a dozen statutes.
The state of liturgy in the Church of Krakow at the time when the diocese was under the leadership of Bishop Zbigniew Oleśnicki was not the best. However, the documents that have survived testify not only to its shortcomings and negligence, but also to the efforts and endeavours of this bishop to constantly improve the liturgy and raise the level and qualifications of its performers. Examples of this are the famous Tractatus sacerdotalis by Mikołaj of Błonie and, above all, the Speculum sacerdotum by Andrzej of Kokorzyn. His treatise ('Mirror') gives an interesting 'reflection of the level of the priests he addresses, with its glories and shadows'. It was born as a wise and mature response of the Bishop to the serious practical problems of the celebration of the Liturgy and is, unfortunately, an illustration of the low theological knowledge of the clergy and the numerous abuses committed by them in the Liturgy. The situation at that time concerning the celebration of the liturgy in the diocese of Krakow and the Bishop's involvement in this matter is aptly reflected in the opinion that "the Krakow clergy had not yet reached a high level, it is true, but they were given aids which made it easier for them. The Speculum is one of them".
Bishop Zbigniew Oleśnicki organised liturgical matters both in various minor details and with regard to certain principles, which concerned either general issues or local regulations. Among the problems he dealt with - and which left their traces in the documents of that period - were the following: ordering the subordinate churches to observe the often violated obligation to observe the liturgical customs of the mother church, i.e. the cathedral; reminding of the principle of the compatibility of the texts of the Mass and the Breviary liturgy; ordering and changing the liturgical calendar of the diocese of Cracow, and especially the elevation of the feast of St Florian after the introduction of the figure of St Florian. Florian following his inclusion in the list of the patron saints of the whole Kingdom of Poland and the regulation of the celebrations in honour of the saints during Great Lent; changes in the liturgy of the hours and the details of their celebration: Introduction of a votive office of the four patron saints - Adalbert, Wenceslas, Florian and Stanislas - on successive weekdays and facilitation of the practice of reciting the choral prayers "quindecim gradus vivorum" and "gradus mortuorum"; regulations concerning the liturgy of the Mass: a reminder of the obligatory provision for the proper preparation of priests for the celebration of the Mass, the prohibition of much superfluous kneeling during the celebration, the demand that the action of raising the consecrated host be performed in such a way that the faithful, seeing it, can adore it, the provision (renewing the somewhat dramatic decree of Bishop Nanker of 1320) that a Mass which began with singing should also end with singing; the prohibition of mutual confession by priests standing, but only kneeling as an expression of humility; numerous interventions on processions as a popular form of worship: The introduction in 1443 of numerous interventions regarding processions as a popular form of worship: Introduction in 1443 of propitiatory processions with relics, litanies and psalms on Mondays, Wednesdays and Fridays of each week for the war with Turkey; permission to hold a procession with the Blessed Sacrament three times a year in St Mary's Church in Krakow as a reminder of the former rules of conduct; definition of the order in which priests would walk in processions and an order to wear their proper vestments for all processions; ordering the compilation of the pontifical, i.e. the liturgical book to be used in all processions. He also established the custom that each new bishop should donate a golden chalice for the cathedral and that new members of the chapter should donate twelve marks for the chapel and wine.
The activity of Bishop and Cardinal Zbigniew Oleśnicki in the field of the liturgical life of the Cracow Church was significant in the light of the known and available sources. He showed himself to be a good theologian, concerned about the doctrinal correctness of liturgical celebrations in the first place, he observed and promoted the observance of Church law in liturgical matters, and he showed considerable organisational initiative in the work of perfecting and beautifying the divine service in his diocese. Cardinal Oleśnicki was, as befits such a significant figure in the history of the Church and its historic and widely appreciated role in the life of the whole Christian nation, "sacerdos magnus" et vere "pastor bonus" of the Church of Krakow.