clw_uk wrote:Which is the oldest commentary?
The earliest commentary-like works would be the commentarial content in the Tipiṭaka itself. For example:
• The definitions of terms in the Vinaya Piṭaka.
• The various suttas in which disciples like Sāriputta and Mahākaccāyana expound at length what the Buddha had expounded in brief.
• The Niddesa of the Khuddaka Nikāya (a commentary to two sections of the Suttanipāta). And perhaps also the Paṭisambhidāmagga.
On the other hand, taking "commentary" in the narrow sense of atthakathā, the oldest extant ones are those of Buddhaghosa, closely followed by those of Dhammapāla. The oldest we know of, but which are no longer extant are the Sinhalese texts from which Buddhaghosa was working — the Mahā-atthakathā, the Mahāpaccarī, and the Kuruṇḍī.