楞伽阿跋多羅寶經註解 2.92

2.92

上明離惑、智二障，能入如來所證法門，然非首楞嚴定莫能造詣，故又明四種禪定，蓋非淺無以明深，故兼三種言之。

The above explains that being free from the two obstructions of defilement and jñeya, one can enter the Dharma gates realized by the Tathāgata; however, without the Śūraṅgama samādhi, one cannot attain this. Therefore, he further explains the four kinds of dhyāna. Indeed, without the shallow, one cannot clarify the profound; hence he speaks of the three kinds together with it.