The craft which was exercised without sin before conversion, was no sin after it. Wherefore after his conversion Peter returned to fishing; but Matthew sat not down again for the receipt of custom (ad telonii negotium resedit). For there are some businesses which cannot or can hardly be carried on without sin; and these cannot be returned to after conversion.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Hom. lxxxiv.