The Greek hekatontaetēs appears only in Romans 4:19 in Paul's exposition of Abraham's faith: 'Without weakening in his faith, he faced the fact that his body was as good as dead — since he was about a hundred years old (hekatontaetēs).' The word underscores the biological impossibility that Abraham and Sarah faced — and the theological point that faith counts on God's power, not human capacity.
Romans 4 uses hekatontaetēs as the outer limit of human reproductive capacity — the point at which all natural hope is exhausted. Abraham's faith did not ignore this reality: he 'faced the fact' (Romans 4:19) of his hekatontaetēs status. Biblical faith is not denial of evidence but trust in God despite evidence. The miracle of Isaac is not less miraculous for being acknowledged as biologically impossible. Paul uses this as the paradigm of justifying faith: 'For us also, to whom righteousness will be credited — for us who believe in him who raised Jesus our Lord from the dead' (Romans 4:24). The same God who gave life to Abraham's hekatontaetēs body raised Jesus from the dead.