A lovely little play on words

"prayers are vainly cast upon the air unless hope [(spes)] be added, from which we quietly watch [(expectemus)] for God as from a watchtower [(specula)]."

     John Calvin, Institutes III.xx.12, trans. Ford Lewis Battles (Library of Christian classics 21 (Philadelphia:  The Westminster Press, 1960), 865); COS IV, p. 311 l. 38 ff. ("preces in aerem frustra proiici, nisi spes sit annexa, unde velut e specula Deum quieti expectemus").

     There is a lovely little play on words here.  For specula, -ae (fem.) is two different words in Latin, really:

1. from the verb specio:  a look-out, watchtower.
2. diminutive of spes, which is related to the verb spero (the 1st edition of the Oxford Latin dictionary, though, says spatium):  a little hope, ray of hope.

Far from unique to Calvin undoubtedly, but none the less striking for that.
     Moreover, specto, on which ex(s)pecto (cf. expectemus, "we . . . watch") is built, is itself related to specio, being a frequentative of it:  specio, to look at, behold; specto, to look at carefully, contemplate, observe, watch.