Zech 2:3

“But because in certain passages of Scripture we have learned that some things are done through the cherubim, and other things through the seraphim, whether they do these things by themselves, or whether they are done through the hosts subject to them, which, as is said, receive the names of the greater ones because they come from the greater ones, we do not wish to affirm what we do not prove by clear testimonies. This, however, we know most certainly, that to carry out service from above, some spirits send others, as the prophet Zechariah testifies, who says: Behold, the angel who was speaking in me went forth; and behold, another angel went forth to meet him, and he said to him: Run, and speak to this young man, saying: Jerusalem shall be inhabited without walls. For when an angel says to an angel "Run and speak," there is no doubt that one sends another. Those who are sent are lesser, those who send are greater.”