Srimad Bhagavatam — Tritiya Skandha, Shloka 36
Sāṅkhya: Categories of the Absolute Truth and the Unfolding of Creation
Tattva-vicāra
मृदुत्वं कठिनत्वं च शैत्यमुष्णत्वमेव च । एतत्स्पर्शस्य स्पर्शत्वं तन्मात्रत्वं नभस्वत: ॥ ३६ ॥
mṛdutvaṁ kaṭhinatvaṁ ca śaityam uṣṇatvam eva ca etat sparśasya sparśatvaṁ tan-mātratvaṁ nabhasvataḥ
柔らかさと硬さ、冷たさと熱さ—これらが触の識別属性であり、触は風（ヴァーユ）の微細形（タンマートラ）であると説かれる。
Tangibility is the proof of form. In actuality, objects are perceived in two different ways. They are either soft or hard, cold or hot, etc. This tangible action of the tactile sense is the result of the evolution of air, which is produced from the sky.
FAQs
This verse states that touch (sparśa)—expressed as softness, hardness, cold, and heat—is a subtle element (tanmātra) specifically associated with air (vāyu).
Kapila teaches Devahūti Sāṅkhya analysis of matter, defining each element by its perceivable qualities; here he identifies the touch-quality that characterizes the air principle.
It trains discernment: by observing qualities and their causes, one learns to separate the temporary material field from the eternal self, supporting steadiness in devotion and practice.