As in smaraṇa स्मरण - Remembrance
摩字門，入諸法摩字不可得故
The syllable SMa is a gateway because the SMa of all dharmas cannot be attained.
Kumarajiva
入颯磨字門，悟一切法可憶念性不可得故
The syllable SMa is a gateway because the ability of being remembered (可憶念性) of all dharmas cannot be attained.
- Xuanzang
SMA because remembrance (smaraṇa)
- Conze
SMA the syllable sma [means] all mental phenomena are openings because of the non-recognition of recollection (smaraṇa).
- Jayarava