大毘盧遮那成佛經疏 13.220

13.220

次閻羅印。作三補吒，二風二地屈入掌，令頭聚合，以二空捻二風背節（當第二第三間也），其空指頭稍屈令合，以二空當火指是也（是壇荼印）。

Next is the Yama mudrā. Form a saṃpuṭa, bend the two wind and two earth fingers into the palm so their tips gather together, pinch the joints on the backs of the two wind fingers with the two space fingers (between the second and third joints), and slightly bend the tips of the space fingers together, placing the two space fingers against the fire fingers (this is the daṇḍa mudrā).