Dhammapada Verse 157
The Story of Bodhirajakumara
Once, Prince Bodhi built a magnificent palace for himself. When the palace was finished he invited the Buddha for alms-food. For this special occasion, he had the building decorated and perfumed with four kinds of scents and incense. Also, a long length of cloth was spread on the floor, starting from the threshold to the interior of the room. Then, because he had no children, the prince made a solemn asseveration that if he were to have any children the Buddha should step on the cloth. When the Buddha came, Prince Bodhi respectfully requested the Buddha three times to enter the room.