The Chapter on a Spike
AN 1.41–50 Paṇihitaacchavagga
41. “Mendicants, suppose a spike of rice or barley was pointing the wrong way. If you trod on it with hand or foot, it is impossible for it to break the skin and produce blood. Why is that? Because the spike is pointing the wrong way. In the same way, it is quite impossible for a mendicant whose mind is pointing the wrong way to break ignorance, produce knowledge, and realize extinguishment. Why is that? Because their mind is pointing the wrong way.”