As in KHa (’space element’) ख
呿字門，入諸法虛空不可得故
The syllable KHa is a gateway because one enters the inapprehensibleness of the nature of space of all dharmas.
- Kumarajiva
入佉字門，悟一切法如虛空性不可得故
Xuanzang
佉(上)字門一切法等虛空不可得故。
Amoghavajra
KHA because of that of the sameness of space (ख kha)
- Conze
The syllable KHA is an opening because of the non-apprehension of the
sameness of space (kha-samata) in all mental phenomena
- Jayarava