This article discusses the Marian antiphon Hec est preclarum vas and its place in the liturgy of the Order of St. Birgitta of Sweden using sources from the abbey of Mariënwater/Maria Refugie (a single abbey known under two names in Noord-Brabant, the Netherlands). Hec est preclarum vas originated in the Low Countries in the late Middle Ages and was widely used in different ecclesiastical contexts. It was sung to protect against plague (and other contagious diseases) and unexpected death. Among the Birgittines in Mariënwater/Maria Refugie it gained a short but intense popularity for about seventy years starting in the second half of the seventeenth century, when it was sung as a suffrage after the daily Lady mass Salve sancta parens. A possible reason for introducing this antiphon at Mariënwater/Maria Refugie may have been a plague epidemic or a similar disease that affected the community or benefactors of the abbey. Several plague epidemics are reported in Noord- Brabant during the seventeenth century, and the community itself suffered from plague in the 1630s, but there are no sources that clearly indicate a link between the antiphon and these plague epidemics. The antiphon’s melody and text as found in the sources from Mariënwater/Maria Refugie show that it connects to known variants of the chant in the Low Countries. The article shows how external factors could motivate the introduction of local customs into the Birgittine liturgy of this community.