Chapter 5 · The Yoga of Renunciation · Krishna said
Bhagavad Gita 5.27 — The method of meditation
स्पर्शान्कृत्वा बहिर्बाह्यांश्चक्षुश्चैवान्तरे भ्रुवोः। प्राणापानौ समौ कृत्वा नासाभ्यन्तरचारिणौ ॥
sparśānkṛtvā bahirbāhyāṃścakṣuścaivāntare bhruvoḥ | prāṇāpānau samau kṛtvā nāsābhyantaracāriṇau ||
Meaning
Shutting out outer objects, fixing the gaze between the eyebrows, and making the in-breath and out-breath even within the nostrils —