Abstract
Mother tongue, in this study referring specifically to Indonesian as children's first and dominant daily language, is an important foundation for young children's communication, social interaction, and learning development. From an Islamic perspective, language ability is part of human potential that should be nurtured according to children's nature and developmental stages. However, mother-tongue stimulation at home and in early childhood education settings is often implemented separately, while learning activities do not always begin with children's interests, including children who show stronger interest in a foreign language. This study aims to formulate the BISA Strategy as an interest-based mother-tongue stimulation approach through collaboration between facilitators and parents. The study combines a literature review of primary Islamic sources, the Qur'an and Hadith, together with national and international studies on the home language environment, mother-tongue use in early childhood education, parental involvement, educators' roles, and language stimulation activities, with an empirical illustration involving a parent interview and facilitator observation of a 4-year-5-month-old child. The findings show that the home and school language environment supports children's language development, mother-tongue use increases children's engagement in learning, and parent-facilitator collaboration strengthens continuity of stimulation. The interview and observation revealed that the child's interest in toys and storybooks was used as an entry point for stimulation, foreign vocabulary was consistently paired with Indonesian equivalents, and communication approaches were continuously adjusted, resulting in improved use and understanding of the mother tongue over time. Based on this synthesis, the BISA Strategy is formulated through four operational stages: Building closeness and identifying children's interests, Identifying context-activity-vocabulary, Synergizing facilitator and parent roles, and Observing and adapting continuously. The BISA Strategy is expected to provide meaningful, natural, consistent, and developmentally appropriate mother-tongue stimulation for young children, even when children show interest in foreign languages.