The material body is a gift of the material energy, technically called illusion. Identification with the material body is due to forgetfulness of our eternal relationship with the Lord. For a pure devotee of the Lord like Bhīṣmadeva, this illusion was at once removed as soon as the Lord arrived. Lord Kṛṣṇa is like the sun, and the illusory, external material energy is like darkness.
In the presence of the sun there is no possibility that darkness can stand. Therefore, just on the arrival of Lord Kṛṣṇa, all material contamination was completely removed, and Bhīṣmadeva was thus able to be transcendentally situated by stopping the activities of the impure senses in collaboration with matter. The soul is originally pure and so also the senses. By material contamination the senses assume the role of imperfection and impurity. By revival of contact with the Supreme Pure, Lord Kṛṣṇa, the senses again become freed from material contaminations. SB 1.9.31
In the presence of the sun there is no possibility that darkness can stand. Therefore, just on the arrival of Lord Kṛṣṇa, all material contamination was completely removed, and Bhīṣmadeva was thus able to be transcendentally situated by stopping the activities of the impure senses in collaboration with matter. The soul is originally pure and so also the senses. By material contamination the senses assume the role of imperfection and impurity. By revival of contact with the Supreme Pure, Lord Kṛṣṇa, the senses again become freed from material contaminations. SB 1.9.31