Augustine highlights two aspects of Ambrose’s ministry which seemed to consume him: caring for his congregation and study.
And Ambrose himself, as the world counts happy, I esteemed a happy man, whom personages so great held in such honour; only his celibacy seemed to me a painful course. But what hope he bore within him, what struggles he had against the temptations which beset his very excellencies, or what comfort in adversities, and what sweet joys Thy Bread had for the hidden mouth of his spirit, when chewing the cud thereof, I neither could conjecture, nor had experienced. Nor did he know the tides of my feelings, or the abyss of my danger. For I could not ask of him, what I would as I would, being shut out both from his ear and speech by multitudes of busy people, whose weaknesses he served. With whom when he was not taken up (which was but a little time), he was either refreshing his body with the sustenance absolutely necessary, or his mind with reading. But when he was reading, his eye glided over the pages, and his heart searched out the sense, but his voice and tongue were at rest. Ofttimes when we had come (for no man was forbidden to enter, nor was it his wont that any who came should be announced to him), we saw him thus reading to himself, and never otherwise; and having long sat silent (for who durst intrude on one so intent?) we were fain to depart, conjecturing that in the small interval which he obtained, free from the din of others’ business, for the recruiting of his mind, he was loth to be taken off; and perchance he dreaded lest if the author he read should deliver any thing obscurely, some attentive or perplexed hearer should desire him to expound it, or to discuss some of the harder questions; so that his time being thus spent, he could not turn over so many volumes as he desired; although the preserving of his voice (which a very little speaking would weaken) might be the truer reason for his reading to himself. But with what intent soever he did it, certainly in such a man it was good (Confessions, Book 6, Chapter 3).