Friar Sand, who was the general of shutter beside the Jade Emperor in Heaven, was banished to Liushahe by the Jade Emperor because he accidentally broke the glass lamp at the Flat Peach Conference.

Not only that, the Jade Emperor punished Friar Sand as if he was worried, and let the flying sword pierce Friar Sand's chest every seven days until Guanyin Bodhisattva found someone to fetch Buddhist scriptures from the West.

When Guanyin Bodhisattva crossed the Liusha River, Friar Sand immediately knelt down and asked Guanyin Bodhisattva for help. Guanyin Bodhisattva couldn't bear Friar Sand to lead such a miserable life, so she asked Friar Sand if he would protect Buddhist scriptures from going to the West, and Friar Sand immediately agreed.

In this way, Friar Sand later became the apprentice of Tang Priest. On the way to the Western Heaven to learn Buddhist scriptures, Friar Sand was diligent, but he didn't even like to say a few more words. He led the horse and fed it honestly.

Extended data:

Above the conference, the Tathagata first praised the Tang Priest and his disciples, and sealed the Buddha to Tang Priest and Wukong, because Friar Sand ate the first nine generations of Tang Priest, which hindered the Buddha's process of spreading Buddhist scriptures eastward as soon as possible, and failed to become a Buddha and became an arhat.

When the Liusha River demon, Friar Sand ate nine Buddhist scriptures back and forth. Unlike ordinary people, the heads of these nine Buddhist scriptures can float on the Liusha River with 3,000 weak waters.

Even if Friar Sand can make great contributions to protect Tang Priest's Buddhist scriptures and kill countless demon kings and demons, it is difficult for Friar Sand to become a Buddha.

References:

Baidu encyclopedia-friar sand