大乘起信論裂網疏 3.37

3.37

Therefore the Buddha taught: "All sentient beings from beginninglessness constantly enter nirvāṇa. Bodhi is not a mark that can be cultivated, nor is it a mark that can be generated; it is ultimately unattainable, having no mark of form that could be seen. That which sees marks of form, one should know, is entirely the illusory function that follows defilement, and not the non-empty mark of wisdom-form, because the mark of wisdom is unattainable." As extensively explained in that text.