首楞嚴義疏注經 9.84

9.84

純是禪定善想所感，無有情欲所對，故云獨行無交。尚有色礙，故云未盡形累。

Because they are entirely induced by wholesome thoughts of dhyāna-concentration, without objects of emotional desire confronting them, they are said to 'travel solitary without intercourse'. Because there is still form-obstruction, it is said that they 'have not exhausted bodily encumbrance'.