अयःकाष्ठादिकं यद्वद्वह्निवद्वह्नियोगतः ।भाति स्थूलादिकं सर्वमात्मवत्स्वात्मयोगतः ॥ २० ॥
In plain words
Iron, wood, whatever else you set in the fire — it glows like fire, and it glows only because the fire is touching it. In just that way the gross body and all the rest shine as though they were the Self, and they shine only from contact with the Self you are.
Close to the Sanskrit
Just as iron, wood, and the rest appear like fire through union with fire, so the gross body and the rest — all of it — appears like the Self through union with one's own Self.