The person and work of Thomas Aquinas (1224/5-1274) can primarily be understood through his self-conception as a preaching brother. Therefore, his sermons provide a special access to him and his thinking. Among these, the series of sermons on the Apostles' Creed holds a prominent place, which Thomas likely delivered during Lent in 1273 in Naples. As a personal testimony of his faith, presented in simple and understandable language, the "Collationes in Symbolum Apostolorum" offers a unique insight into his theology and spirituality. Hardly any work of Thomas Aquinas seems more suitable for an initial acquaintance with him.