Srimad-Bhagavatam: Canto 3 - Chapter 1 - Verse 9
सानुबन्धे च देहेऽस्मिन्नकुर्वन्नसदाग्रहम् ।ज्ञानेन दृष्टतत्त्वेन प्रकृते: पुरुषस्य च ॥ ९ ॥
sānubandhe ca dehe ’sminnakurvann asad-āgrahamjñānena dṛṣṭa-tattvenaprakṛteḥ puruṣasya ca
One’s seeing power should be increased through knowledge of spirit and matter, and one should not unnecessarily identify himself with the body and thus become attracted by bodily relationships.
The conditioned souls are eager to identify with the body and consider that the body is “myself” and that anything in relationship with the body or possessions of the body is “mine.” In Sanskrit this is called aham-mamatā, and it is the root cause of all conditional life. A person should see things as the combination of matter and spirit. He should distinguish between the nature of matter and the nature of spirit, and his real identification should be with spirit, not with matter. By this knowledge, one should avoid the false, bodily concept of life.