Nor matters it that Matthew speaks of an ass and its foal, while the others say nothing of the ass; for when both may be conceived, there is no variance even though one relate one thing, and another another, much less where one relates one thing, another both.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: de con. Ev. lib. ii. cap. 66.