Ambrose of Milan

Now what was the guilt which Balaam incurred, but that he spoke one thing, and designed another? For God requires a clean vessel, not one defiled by uncleanness and pollution. Balaam therefore was tried, not approved, for he was full of deceit and treachery. …

Letters 41-50 ↗

Gregory the Dialogist

The sick are to be admonished to consider how great health of the heart is in bodily affliction, which recalls the mind to knowledge of itself, and renews the memory of infirmity which health for the most part casts away, so that the spirit, which is carried out of itself into elation, may be reminded by the smitten flesh from which it suffers to what condition it is subject. Which thing is rightly signified to Balaam (had he but been willing to follow obediently the voice of God) in the very retardation of his journey. …

The Book of Pastoral Rule, Part 3 ↗