Gregory the Great
Catena Aurea · Matthäusevangelium 18
Take heed that ye despise not one of these little ones; for I say unto you, That in heaven their angels do always behold the face of my Father which is in heaven. For the Son of man is come to save that which was lost. How think ye? if a man have an hundred sheep, and one of them be gone astray, doth he not leave the ninety and nine, and goeth into the mountains, and seeketh that which is gone astray? And if so be that he find it, verily I say unto you, he rejoiceth more of that sheep, than of the ninety and nine which went not astray. Even so it is not the will of your Father which is in heaven, that one of these little ones should perish.
(Mor. ii. 3.) And therefore the Angels always behold the face of the Father, and yet they come to us, for by a spiritual presence they come forth to us, and yet by internal contemplation keep themselvesthere whence they come forth; for they come not so forth from the divine vision, as to hinder the joys of inward contemplation.