As in the 49th Daiku-kyo Sutra (大空経) of the Chu Agon-kyo Sutra (The Middle-Length Agama Sutras), there is a description that 'make Shakyamuni the base of Buddhism and hoshu. Buddhism should be preached by Shakyamuni,' and in the first of the Zo Agon-kyo (Miscellaneous Agama Sutra) there is a description that 'make Shakyamuni hoshu, a guide and fuku (覆),' it was a honorific title of Shakyamuni, a master of Shobo (the True Dharma of Buddhism).
中阿含経第49大空経に「世尊（＝釈迦）を法の本と為し、世尊を法主と為す。法は世尊に由る」と記され、同じく雑阿含経第1に「世尊を法主と為し、導と為し、覆と為す」と記され、正法（仏教の正しい教え）の主である釈迦を尊んだ呼び方であった。