But we must believe that the disciples of Christ were already baptized themselves, either with John’s baptism, or, as is more probable, with Christ’s. For He who had stooped to the humble service of washing His disciples’ feet, had not failed to administer baptism to His servants, who would thus be enabled in their turn to baptize others.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Ad Seleuciam Ep. xviii.