What is Sutra
The name sutra (Sanskrit for "thread") in Buddhism originally was given only to the sermons of the historical Buddha. The sutras were recited from memory by the Buddha's disciple Ananda at the First Buddhist Council. From Ananda's memory they were collected in the part of the Tripitaka called the Sutra-pitaka.
The teachings of the Buddha are recorded in sutras. They are written in Pali and Sanskrit. Many are preserved in Chinese and Tibetan translations. Some of the widely-known sutras are the Flower Adornment Sutra, Diamond Sutra, the Heart Sutra, Perfect Enlightenment Sutra, and the Lotus Sutra. The sutras were written in prose style. The format was simple without metrical or poetic structure. The opening line is always "Thus have I heard", indicating what follows after it are the actual words of the Buddha. The "I" was Venerable Ananda, a disciple of the Buddha. He was famous for his memory and contribution to retaining most of the sutras.
Ananda spoke the words “Thus have I heard” for four reasons:
1. To resolve the assembly’s doubts.
2. To honor the Buddha’s instructions.
3. To put an end to disputes.
4. To distinguish Buddhist Sutras from the writings of other religions.
Reading the sutras is just like letting the Buddha speak directly to us. Therefore, to practise Buddhism, one should chant sutra regularly.