太子瑞應本起經 2.38

2.38

「佛還樹下，道見棄弊衣，取欲浣之。天帝知佛意，即到頞那山上，取正四方成治好石，來置池邊，白佛言：『可用浣衣。』佛欲曬衣，天帝復行取六方石來，給曬衣。

"When the Buddha returned beneath the tree, he saw along the road a discarded, worn-out robe, and took it, wishing to wash it. Śakra, knowing the Buddha's intention, immediately went to Mount *Ana, took a square, smoothly finished fine stone, brought it, placed it beside the pond, and said to the Buddha: 'This may be used for washing the robe.' When the Buddha wished to dry the robe, Śakra went again, fetched a six-sided stone, and supplied it for drying the robe.