Creedal rulings are described as uṣūliyyah (foundational) and iʿtiqādiyyah (concerning belief). The first term points to truths that underlie a sound religious understanding; the second identifies the mode of inquiry as affirmation and belief.
Divine unity and prophethood are foundational claims, not merely procedural details in worship. By contrast, the detailed elements of prayer, the particulars of zakat payment and the conditions of a sale are normally examined in practical jurisprudence.
This is an analytical distinction, not a claim that religious practice has no relation to faith.