10 This, then, my brethren, John learned. What John learned by means of the dove let us also learn. For the dove did not teach John without teaching the Church, the Church to which it was said, “My dove is one.” Let the dove teach the dove; let the dove know what John learned by the dove. The Holy Spirit descended in the form of a dove. But this which John learned in the dove, wherefore did he learn it in the dove? For it behooved him to learn, and perhaps it did not so much behoove him to learn as to learn by the dove. What shall I say, my brethren, concerning the dove? Or when will faculty of tongue or heart suffice to speak as I wish? And perchance, my wish falls short of my duty in speaking; even if I were able to speak as I wish, how much less am I able to speak as I ought? I could wish to hear one better than myself speak this, rather than speak of it to you.
Source: Tractates on the Gospel of John (New Advent)