摩訶止觀 4.126

4.126

二、同行者，行隨自意及安樂行，未必須伴；方等、般舟行法，決須好伴，更相策發，不眠不散，日有其新；切磋琢磨，同心齊志，如乘一船；互相敬重，如視世尊。是名「同行」。

Second, the fellow practitioner: when practicing according to one's own intent or the practice of ease, a companion is not strictly necessary; but in the Vaipulya and Pratyutpanna practices, a good companion is definitely required, mutually spurring each other on, neither sleeping nor scattering, renewing each day; cutting and polishing, of one mind and equal resolve, like riding in a single boat; mutually respecting each other, as if looking upon the World-Honoured One. This is called the "fellow practitioner."