The Tso-chuan records that the sons must perform a rite for the soul of the deceased before a wooden spirit tablet can serve as a symbol of the ancestor's spirit.
據左傳的記載，凡君薨，孝子需舉行致死者之神靈於祖廟的祭禮，稱之為「祔祭」，經祔祭後，木主才被賦予象徵祖靈的意義。