This paper investigates the role of Spanish vernacularisations of Jewish prayer books (siddurim) in the Early Modern period from a twofold perspective. First, it examines their function as a linguistic vehicle that enabled former conversos - lacking knowledge of Hebrew and wishing to return to Judaism - to understand the meaning of the prayers and to participate more consciously in communal worship conducted in Hebrew. Full comprehension of the liturgical text fostered a deeper spiritual engagement and a renewed relationship with the Divine. Building on this premise, the paper hypothesizes the existence - for some prayers - of relatively stable or "standard" translations circulating among Sephardi communities. Such shared versions may have strengthened communal cohesion through familiarity with common liturgical formulas and the perception of a more stable spiritual connection with the Divinity. In this context, translation was a practical instrument for reintegrating former conversos into the social and religious fabric of the Sephardi diaspora. This process must be analysed considering the mobility that characterized these communities, whose rabbis and leading figures frequently moved from one centre to another. Secondly, the paper explores the presence of vernacularized prayers in Jewish treatises of the Early Modern period, with a special focus to works produced in the first half of the seventeenth century - marked by the increasing of the phenomenon of teshuvah, understood here as a return to Judaism, and by a growing demand for texts facilitating the reintegration of former conversos. The treatise "Thesoro de Preceptos" is a case study for examining the social role of translation in the liturgical sphere. Familiarity with vernacular versions of major prayers may have reinforced not only local communal identity but also bonds among geographically distant Sephardi communities, contributing to the maintenance of a broader "pan-Sephardi" sense of spiritual unity.