成唯識論述記 7.144

7.144

述曰：第三子門。下上尋、伺互得緣上下，境界寬故。欲界者，緣上二界；色界者，緣上下二界地。

The Commentary states: The third sub-door. Investigation and analysis of the lower and higher are mutually able to cognize the higher and lower, because their cognitive sphere is broad. Those of the desire realm cognize the two higher realms; those of the form realm cognize the realms and stages of both higher and lower.