《大唐大慈恩寺三藏法師傳》 (T 2053) – a Tang Dynasty (唐) biography (傳) of Xuánzàng (aka “the Dharma Master 三藏法師傳 of the great Ci’en Temple 大慈恩寺”) by 慧立 Huìlì and 彥悰 Yàncóng from about 688 CE.
- Beal, S. (1914.) The Life of Hiuen-Tsiang. By the Shamans Hwui Li and Yen-Tsung. London: Kegan Paul, Trench, Trubner & Co.
- Li Rongxi (1995) A Biography of the Tripiṭaka Master of the Great Ci’en Monastery of the Great Tang Dynasty. Numata Center for Buddhist Translation and Research.
There are two references to the 《心經》 in the Biography.
1. Xuánzàng Receives and Recites the Xīnjīng
This occurs at T 50.224.b.7 in the context of Xuánzàng leaving China.
[224.a 23] 至曉，法師食訖，祥使人盛水及麨餅自送至十餘里。云：「師從此路徑向第四烽，彼人亦有善心，又是弟子骨肉，姓王名伯隴，至彼可言弟子遣師來。」泣拜而別。既去，夜到第四烽，恐為留難，欲默取水而過。至水未下間，飛箭已至，還如前報，即急向之，彼亦下來。入烽，烽官相問，答：「欲往天竺，路由於此，第一烽王祥校尉故遣相過。」彼聞歡喜留宿，更施大皮囊及馬、麥相送。云：「師不須向第五烽。彼人疎率，恐生異圖。可於此去百里許，有野馬泉，更取水。從是已去，即莫賀延磧，長八百餘里，古曰沙河，上無飛鳥，下無走獸，復無水草。」是時顧影唯一，但念觀音菩薩及《般若心經》。
 At first when the Master of the Law was dwelling in Shuh he saw a diseased man whose body was covered with ulcers, his garments tattered and filthy. Pitying the man he took him to his convent, and gave him clothing and food; the sick man, moved by a feeling of deep gratitude, gave to the Master of the Law this little Sûtra-book, and on this account he was in the habit of reciting it continually. Arriving at the Sha-ho1 as he passed through it, he encountered all sorts of demon shapes and strange goblins, which seemed to surround him behind and before. Although he invoked the name of Kwan-Yin, he could not drive them all away; but  when he recited this Sutra2 at the sound of the words they all disappeared in a moment. Whenever he was in danger, it was to this alone that he trusted for his safety and deliverance.
That is, the Sandy desert (Sand-river)
This Sûtra is regarded by the Chinese as a Mantra, or charm, to the present day. One of my native teachers (when I was in China), although he professed to despise Buddhism, used to repeat it from memory.
Note that “Shuh” 在 (Pinyin Shǔ) is modern day Sichuan 四川.
My feeling is that Li’s translation of this passage is less reliable. For example, he translated in part: “With a feeling of pity, he took the man to his monastery and gave him money to purchase clothes and food.” (26). But the text makes no mention of money. It seems to say, per Beal, that Xuánzàng gave (施) the man clothing (衣服) and food and drink (飲食) and here “gave” has a sense of donating.
There are two points here. The first is that Xuánzàng recites the Xīnjīng to protect himself from demons, which is typical of how the text is conceived of. The second is that he received the text from a sick man dressed in rages (and thus also poor). Since it is unlikely that a poor, sick man would know a Sanskrit sutra, and since we know that the sutra was composed in Chinese, we can say that in all likelihood the sutra he gave Xuánzàng was already in Chinese.
2. Xuánzàng Gifts the Text.
輒敢進金字《般若心經》一卷并函 (T 50.272b.12)
“I dare to offer a copy of the Insight Heart Sutra in gold letters, one scroll with a case.” [My translation]
From the text we can deduce that this happened on 永徽六年十二月五日 i.e. 6 January 656. This is extremely important, because it appears to be the earliest literary reference to the Heart Sutra. And it occurs well before Xuánzàng began to translate the collection of Prajñāpāramitā Sūtras that be bought with him from India. He left the capital in Changan for 顯慶四年十月, Nov 659 for 玉華宮 Yuhua Gong, or Palace of Jade Flowers about 100 km North. He began translating on 顯慶五年正月一日 16 Feb 660 and finished 龍朔三年十月二十日 15 Nov 663. Then died 麟德一年二月五日 7 March 664.
There is curiously little discussion of this important passage and the date in the literature.