Gargya said: 'The person that is in the lightning (and in the heart), that I adore as Brahman.' Agatasatru said to him: 'No, no! Do not speak to me on this. I adore him verily as the luminous.' Whoso adores him thus, becomes luminous, and his offspring becomes luminous.

In plain words: Gargya said he worships the person in lightning as Brahman. The king said he already honors that one as shining, and whoever does so becomes bright, and so do his children.