Augustine of Hippo

(De Civ. Dei, xx. 9.) Otherwise, unless your righteousness exceed the righteousness of the Scribes and Pharisees, that is, exceed that of those who break what themselves teach, as it is elsewhere said of them, They say, and do not; (Mat. 23:3.) just as if He had said, Unless your righteousness exceed in this way that ye do what ye teach, you shall not enter the kingdom of heaven. We must therefore understand something other than usual by the kingdom of heaven here, in which are to be both he who breaks what he teaches, and he who does it, but the one least, the other great; this kingdom of heaven is the present Church. In another sense is the kingdom of heaven spoken of that place where none enters but he who does what he teaches, and this is the Church as it shall be hereafter.