The light in a church amplified the sacred element of the building. The foundations connected with supplying candles and keeping churches lit were supposed to help in attaining redemption. Based on the literature and archival sources (such as testaments and guild records) the author has analysed the role of light in the pious foundations of individuals and fraternities in the parish churches of Prussian cities in the 14th-15th c. The article discuses the issue of wax trade and the funding necessary to provide fraternity chapels with festive illumination. In order to obtain the source of lighting guilds and fraternities made their members pay fines for breaking community rules in wax. In the parish churches of Prussian cities it was a common practice to make separate foundations providing the church with lighting or to include such a proviso in the foundation of masses, altars or chapels; such foundations were actually widespread across Europe. Mentions concerning the keeping of the light are often found in sources relating to the veneration of Corpus Christi. The cult was commonly connected with founding an eternal lamp, for which it was necessary to provide 6-8 marks (grzywny) per annum. The development of the cult in the Teutonic Order state, its roots and practices, are worthy of further detailed research. The yearly cost of lighting an altar during the mass rarely exceeded 2-3 marks. Light was undoubtedly an important element of funeral ceremonies, therefore testaments and fraternity rules often contain instructions regarding the use of candles at burials.