So then the Son speaks, the Holy Spirit teaches: when the Son speaks we take in the words, when the Holy Spirit teaches, we understand those words. The whole Trinity indeed both speaks and teaches, but unless each person worked separately as well, the whole would be too much for human infirmity to take in.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Tract. lxxvii. 2