From the Rule, chapter IX, section 3:
Moneo quoque et exhortor eosdem fratres, ut in praedicatione, quam faciunt, sint examinata et casta eorum eloquia (cf. psalm 11:7 and 17:31, Vulgate), ad utilitatem et aedificationem populi, annuntiando eis vitia et virtutes, poenam et gloriam cum brevitate sermonis; quia verbum abbreviatum fecit Dominus super terram. (cf. Romans 9:28, Vulgate)
"I warn and exhort the brothers that in the preaching that they do, their words be considered and chaste, for the usefulness and edification of the people, announcing to them vices and virtues, punishment and glory with a brief word [e.g. 140 characters]; for the Lord made a short word on earth."