In plain words
Third, śāstra. It wrote down the rule of how man, who has the four āśramas, brahmacarya, gṛhastha, vānaprastha and sannyāsa, must conduct himself, and in what way he himself must carry out his duty in each kind of work. Not only this: for rites such as jātakarma, nāmakaraṇa and marriage too, they have laid down what man must observe, that is, the karmas enjoined in them and the karmas forbidden. The rites such as yajña and yāga, performed for the good of the world and for the sacred reform of man's life, are also bound up with this śāstra. Only when all the vows to be given at the wedding, the groom's to the bride and the bride's to the groom, are well laid down will this Dharma of the householder go well, chattering and laughing merrily, hung with the green festoons of an everlasting festival. All such vows, all such promises, are made today only for the moment; people do not hold them as vows pressed close to their hearts. That is why man, in the Dharma of the householder, falls into many hardships, sorrows and losses. Only when we look on the promises made with Agni as witness and the heart as witness as equal to life itself, and act by them, do we gain a sacred result as well.
O tongue, knower of tastes, lover of sweetness, I tell you the truth, the good, the highest: recite the sweet syllables Govinda, Dāmodara, Mādhava.
That is, man has two eyes. With them man can see two things. He has two ears. He can hear both good and bad. But the tongue is one. One must stand by one word. When people act against the word they have given, they become like the two-tongued poisonous worm. So only when man keeps to one word is there room in his life for harmony, for oneness, and for going on to divinity.
Satyaṃ vada, dharmaṃ cara: these are the sacred eyes in the culture of Bhārata. One must speak Satya. One must do Dharma. That is why Satya is one, not two. Truth is one not two. The principle ekam eva advitīyaṃ brahma too has proclaimed this very Satya.