This study aims to establish the semantic range of pieίsigmaτις ('faith') in fourth century Christian discourse using the preaching of John Chrysostom as a source base. Against previous scholarship which sees pieίsigmaτις as primarily a cognitive or propositional term referring to belief, this study uses a close examination of Chrysostom's preaching to argue that the relational nature of the term was central to its significance for fourth century preaching as Christians considered their own faith and biblical texts. Chrysostom uses the reciprocal, relational character of pieίsigmaτις to emphasise loyalty, trust and obedience to God through metaphors based upon the military, economic and household contexts of late antiquity. This study further shows that Chrysostom in turn uses these aspects of pieίsigmaτις to seek to influence the everyday life of his congregation, whether to support existing behaviour (such as obedience to the emperor, or husbands, or the bishop) or to seek to transform behaviour (such as encouraging the rich to give to the poor, or masters to treat slaves better). This contextual understanding of pieίsigmaτις therefore sheds light on how the relationship with God both informed and was informed by the everyday human relationships of the congregation. The study overall demonstrates the necessity of understanding Chrysostom's view of pieίsigmaτις as belonging within a reciprocal relationship, enabling a new view of Chrysostom's preaching, faith and late antiquity to emerge.