On one occasion the Blessed One was staying near Vesali at the Gabled Hall in the Great Forest. Then in the early morning, Ven. Ananda, having put on his robe and carrying his bowl and outer robe, went into Vesali for alms. He saw a large number of Licchavi boys practicing archery in the stadium building. From a distance they were shooting arrows through a tiny keyhole without missing, one right after the other. On seeing this, the thought occurred to him, "How trained these Licchavi boys are, how well-trained these Licchavi boys are, in that from a distance they can shoot arrows through a tiny keyhole without missing, one right after the other!"
Then, having gone for alms in Vesali, after his meal, returning from his alms round, Ven. Ananda went to the Blessed One and, on arrival, having bowed down to him, sat to one side. As he was sitting there, he said to the Blessed One: "Just now, lord, in the early morning, having put on my robe and carrying my bowl and outer robe, I went into Vesali for alms. I saw a large number of Licchavi boys practicing archery in the stadium building. From a distance they were shooting arrows through a tiny keyhole without missing, one right after the other. On seeing this, the thought occurred to me 'How trained these Licchavi boys are, how well-trained these Licchavi boys are, in that from a distance they can shoot arrows through a tiny keyhole without missing, one right after the other!'"
"What do you think, Ananda: Which is harder to do, harder to master — to shoot arrows through a tiny keyhole without missing, one right after the other, or to take a horsehair split into seven strands and pierce tip with a tip?"[1]
"This, lord, is harder to do, harder to master — to take a horsehair split into seven strands and pierce tip with a tip."
"And they, Ananda, pierce what is even harder to pierce, those who pierce, as it actually is present, that 'This is stress'; who pierce, as it actually is present, that 'This is the origination of stress'... 'This is the cessation of stress'... 'This is the path of practice leading to the cessation of stress.'
"Therefore, Ananda, your duty is the contemplation, 'This is stress... This is the origination of stress... This is the cessation of stress.' Your duty is the contemplation, 'This is the path of practice leading to the cessation of stress.'"
See also: SN 56.44