Yoga Sūtra Chapter Two verse 49

तस्मिन् सति श्वासप्रश्वास्योर्गतिविच्छेदः प्राणायामः ॥४९॥

tasmin-sati-śvāsa-praśvāsayoḥ gati-vicchedaḥ prāṇāyāmaḥ ||49||

Being in this,
dividing the motion of the exhalation and the inhalation
is extending the breath.

tasmin - in thissati - beingśvāsa - breathing or aspiration; hissing, snorting, panting; affection of the breath, hard breathing, asthmapraśvāsā - breathing in, inhaling; breath, respiration;gati - going, moving, gait, deportment, motion in generalviccheda - cutting asunder, cleaving, piercing, breaking, dividing, separation; interruption, discontinuance, cessation; caesura, pause in a verseprāṇāyāma - extending the breath

Commentaries and Reflections

Commentary by TKV Desikachar:

Prāṇāyāma leads to this. Pratyāhāra,
to see without the senses distracting or pulling the mind,
and Dhāraṇā –
To see without the mind losing itself,
because of colouring or expectations.
Dhyānam arises out of this.”