In that God sometimes delays His gifts, He but recommends, and does not deny them. For that which is long looked for is sweeter when obtained; but that is held cheap, which comes at once. Ask then and seek things righteous. For by asking and seeking grows the appetite of taking. God reserves for you those things which He is not willing to give you at once, that you may learn greatly to desire great things. Therefore we ought always to pray and not to fail.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Serm. 61. 5