Which early Church Father discussed that all people are saved by means of one covenant of grace?

Justin Martyr is recognized for articulating a view that emphasizes the unity of salvation through one covenant of grace, which was a significant theme in early Christian thought. He argued that God's providential plan for salvation encompasses all of humanity, suggesting that grace is accessible to all people irrespective of their specific covenantal context. This universal approach paved the way for later theological discussions around grace and salvation, influencing subsequent Church Fathers' understanding of covenant theology.

The concepts presented by Augustine of Hippo, Irenaeus of Lyons, and Clement of Alexandria do touch on covenant and grace but do not explicitly focus on the notion of a singular covenant of grace for all humanity in the same way that Justin Martyr does. Their contributions often involve more nuanced discussions about original sin, redemption, and the nature of God's covenants, but they don't encapsulate the same inclusive view that characterizes Justin Martyr's perspective. This makes Justin's approach distinct and significant in early Church dialogues about salvation.