Digha Nikaya 1:760
SUJATOVesāliyaṁ piṇḍāya caritvā pacchābhattaṁ piṇḍapātapaṭikkanto nāgāpalokitaṁ vesāliṁ apaloketvā āyasmantaṁ ānandaṁ āmantesi:
Then, after the meal, on his return from almsround, he turned to gaze back at Vesālī, the way that elephants do. He said to Venerable Ānanda: