c. 403–404 · John Chrysostom, Homilies on the Epistle to the Hebrews 21.4
O what an expression has he used, in saying, “an evidence of things not seen.” For [we say] there is “evidence,” in the case of things that are very plain. Faith then is the seeing things not plain (he means), and brings what are not seen to the same full assurance with what are seen. So then neither is it possible to disbelieve in things which are seen, nor, on the other hand can there be faith unless a man be more fully assured with respect to things invisible, than he is with respect to things that are most clearly seen. For since the objects of hope seem to be unsubstantial, Faith gives them substantiality, or rather, does not give it, but is itself their substance. For instance, the Resurrection has not come, nor does it exist substantially, but hope makes it substantial in our soul. This is [the meaning of] “the substance of things.”