This paper examines the role of sacred languages in family language policy (FLP), with a particular focus on case studies from France and Finland. While recent scholarships on FLP have extensively explored heritage language maintenance in diasporic contexts, the position and maintenance of sacred languages within family linguistic ecosystems remains understudied. This research aims to address this gap by investigating how sacred languages, particularly Qur’anic Arabic, are maintained and transmitted in diaspora communities facing linguistic pressures from dominant languages such as French, Finnish, and English. The study employs a mixed-methods approach, combining questionnaire data with longitudinal observational data of Urdu-speaking and Pakistani background students of Inalco in France, and a two-year case study of a family in Finland. The current findings suggest that the Arabic language plays a crucial role in maintaining religiosity within the home environment, often prioritized over heritage language acquisition and maintenance.