Ud 5:10 Cūḷa Panthaka (Panthaka Sutta)
I have heard that on one occasion the Blessed One was staying near Sāvatthī at Jeta’s Grove, Anāthapiṇḍika’s monastery. And on that occasion Ven. Cūḷa Panthaka was sitting not far from the Blessed One, his legs crossed, his body held erect, with mindfulness established to the fore. The Blessed One saw Ven. Cūḷa Panthaka sitting not far away, his legs crossed, his body held erect, with mindfulness established to the fore.
Then, on realizing the significance of that, the Blessed One on that occasion exclaimed:
With steady body,
–whether standing, sitting, or lying down1–
a monk determined on mindfulness
gains one distinction
Having gained one distinction
he goes where the King of Death
1. There’s a slight paradox in this verse in that the word for “steady” (ṭhita) can also mean “standing.” Thus when the body is steady and unmoving, it is “standing” regardless of its posture.