Translator's note: See the introductory note to SN 1.38.
I have heard that on one occasion the Blessed One was staying near Rajagaha at the Maddakucchi Deer Reserve. Now at that time his foot had been pierced by a stone sliver. Excruciating were the bodily feelings that developed within him — painful, fierce, sharp, wracking, repellent, disagreeable — but he endured them mindful, alert, & unperturbed. Having had his outer robe folded in four and laid out, he lay down on his right side in the lion's posture — with one foot placed on top of the other — mindful & alert.
Then Mara the Evil One went to the Blessed One and recited this verse in his presence:
[The Buddha:]I lie here, not in a stupor, nor drunk on poetry. My goal attained, I am sorrow-free. All alone in a secluded lodging, I lie down with sympathy for all beings. Even those pierced in the chest with an arrow, their hearts rapidly, rapidly beating: even they with their arrows are able to sleep. So why shouldn't I, with my arrow removed? I'm not awake with worry, nor afraid to sleep. Days & nights don't oppress me. I see no threat of decline in any world at all. That's why I sleep with sympathy for all beings.
Then Mara the Evil One — sad & dejected at realizing, "The Blessed One knows me; the One Well-Gone knows me" — vanished right there.