Bhagavad Gita 17.3

Every person's faith conforms to their nature. By nature, they are full of faith. They are, in fact, what their faith makes them.

सत्त्वानुरूपा सर्वस्य श्रद्धा भवति भारत।श्रद्धामयोऽयं पुरुषो यो यच्छ्रद्धः स एव सः॥

sattvānurūpā sarvasya śraddhā bhavati bhārata|śraddhāmayo'yaṃ puruṣo yo yacchraddhaḥ sa eva saḥ||

English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).