Vaisesika Sūtra 2.1.28

द्रव्यत्वनित्यत्वे वायुना व्याख्यायते ॥२८॥

dravyatvanityatve vāyunā vyākhyāyate ॥28॥

[द्रव्यत्व नित्यत्वे वायुना व्याख्यायते॥
dravyatva = substance-ness; nityatve = permanence-ness of; vāyunā = by air; vyākhyāyate = it is explained;]

It is said that the permanence of substance-ness is because of air.