[46] "Bhikkhus, suppose there were a pool of water, turbid, stirred up, and muddy. A man with good eyes, standing on the bank, would not see the oysters and shells, the gravel and pebbles, or the shoals of fish moving about and staying still in it. For what reason? Because of the turbidity of the water, bhikkhus. So too, bhikkhus, that a bhikkhu with a turbid mind (citta) will know his own good, or know the good of others, or know the good of both, or realize a distinction in knowledge (ñāṇa) and vision worthy of the noble ones, surpassing the human state — this is impossible. For what reason? Because of the turbidity of the mind, bhikkhus."
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.