成唯識論演祕 1.3

1.3

不定姓人歸於佛法，智解淺深，三時悟異，名曰「三機」。非定別三，唯對不定立三時故。

When persons of indeterminate lineage take refuge in the Buddha-Dharma, the depth or shallowness of their understanding and their awakenings in the three periods differ; these are called the "three capacities." It is not that there are definitely three separate categories; it is only in reference to the indeterminate that the three periods are established.