Second episode/adhyaya – Sankhya yoga
nāsato vidyate bhāvo
na—never; asataḥ—of the nonexistent; vidyate—there is; bhāvaḥ—endurance; na—never; abhāvaḥ—changing quality; vidyate—there is; sataḥ—of the eternal; ubhayoḥ—of the two; api—verily; dṛṣṭaḥ—observed; antaḥ—conclusion; tu—but; anayoḥ—of them; tattva—truth; darśibhiḥ—by the seers.
Text Source – “http://prabhupadabooks.com/bg”
Seers have concluded by observing both, that for the asatah(non existent body) there is no endurance, and for the Satah(eternal soul) there is no change.
Lord is saying even seers, who have observed the nature of both body and soul, have authenticated that the transient nature of the mind/body has no existence, while the soul is indestructible.
These days the trend is to say all the Hindu customs have some “scientific significance”. We don’t know for ourselves, we haven’t explored or experienced them, yet we believe it to be true because we put our faith on some scientist who has proven it somewhere.
Similarly believe that the transient nature of the body/mind is non-existent while the soul is indestructible, because seers(who have observed this) have concluded that. So have faith in the seers and just believe it to be true.
Continuing the thought form the previous verses – the changing qualities like sukha-dukha, sheeta-ushna(hot-cold) are transient, hence they are non-existent. So learn to bear them(thinking these are not existent). While knowing that the unchanging atma(soul), which is not subjected to kaumaram-yavvanam-jara(infant-youth-old age) is never changing, hence eternal.