The original expression, (ην υποχωρων εν ταις ερημοις, και προσευχομενος), implies that he frequently left the large groups to find solitude and pray.
Though no one was ever more busily employed than he was, or did so much good in public as he did, yet he found time for pious and devout retirement: not that he needed to avoid either distraction or ostentation; but he meant to set us, who have need, an example, so to order the circumstances of our devotion as to guard against both.
It is likewise our wisdom so to order our affairs, that our public work and our secret devotions may not intrench upon, or interfere with each other. Observe, reader, private prayer must be performed secretly; and how much soever we have to do in the best business in this world, we ought to have stated times for it, and steadily to attend to them.
[Excerpt from the Benson Commentary]