首楞嚴義疏注經 1.86

1.86

非禪不慧，故先入定為後軌也。即敷尼師壇靜然安坐，如《金剛》、《法華》皆先入定，後方始說，常法爾也。

Without dhyāna there is no wisdom, so he first entered samādhi to serve as a model for those who follow. That is, having spread out his sitting mat (niṣīdana), he sat peacefully and quietly; just as in the Diamond Sūtra and Lotus Sūtra, he first entered samādhi, and only afterward began to speak; this is the constant rule of the Dharma.