The best testimony to the claim that the Smrtis are founded on the Vedas is provided by the words of mahakavi(great poet). Sankara, Ramanuja and Madhva, the founders of our religio-philosophical systems, proclaim that our dharmasastras are in accord with the Vedas. But they had, each of them, a doctrine to establish. Besides they had also the goal before them of preserving the tradition and they would not naturally go against it. With a poet it is different. He has no doctrine to establish, no belief to promote. He speaks what he feels to be the truth since he does not have to lend his support to any particular concept or system.
The greatest of the mahakavis, Kalidasa, makes a reference to the Smrtis in his Raghuvamsam.
As all of you know, Dasaratha was the father of Rama. Dasaratha's father was Aja and Aja's father was Raghu. Rama was named Raghurama after his great-grandfather. We do not often come across "Dasarathi" among the names of Rama. Usually one is named after one's grandfather. But Rama did not take the name of Aja and is better known after his great-grandfather. Raghu had such fame and glory. The name Raghava also means one belonging to the family of Raghu.
Raghu's father was Dilipa. For long he did not have a son. The guru of Dilipa's family was Vasistha. Dilipa approached him and said to him: "Svamin, I don't have a child. Bless me that my family will continue and prosper. " Vasistha had a cow called Nandini, the daughter of Kamadhenu. The sage asked the king to look after the cow and worship her with faith. He blessed Dilipa thus: "A son will be born to you. " Think of it, a king was asked to look after the cow. How humble he must have been.
Dilipa took charge of the cow right away. Like a cowherd he took Nandini to the forest, grazed her, bathed her and looked after with devotion. He carried a bow with just one arrow to protect her from wild beasts. He scratched the cow, stopped on the way if she stopped, lay down if she lay down, walked if she walked. If we sit down our shadow too will seem to sit down, if we stand up so too our shadow will seem to stand up, if we run then too our shadow will seem to run. "Chayeva tam bhupatiranvagacchat, ", says Kalidasa. Dilipa followed the cow like a shadow.
Every day, as Dilipa took the cow to graze, his wife Sudhaksina would follow him to some distance and then return home. Very religiously she would send her husband out with Nandini and wait in the evening for them to return from the forest. Sudhaksina kept caring for Dilipa and, if the king followed Nandini like a shadow, she too followed him in turn like a shadow.
The duties of a Pativrata are described by Janaka during the marriage of his daughter Sita to Rama. He says to Rama: "My child Sita will follow you like a shadow (chayevanugata)". This is in Valmiki Ramayana. Kalidasa retells the story of Rama that Valmiki has told. He speaks about Lava and Kusa who came after Rama and also about Rama's predecessors. And he gives to his great poetical work the title of Raghuvamsam after Rama's great-grandfather Raghu of unsurpassed fame. Verily, to speak of this family is to sanctify one's speech.
In the passage describing how Sudhaksina followed Dilipa as he goes grazing the cow, the poet makes a reference to the sages creating the Smrtis. He does so not in pursuance of any doctrine, not also after any deliberation. He speaks spontaneously about the Smrtis, unpremeditatedly. The poet describes how Sudhaksina follows the cow to some distance. Nandini is in the front and Sudhaksina walks behind. The cow raises a little dust with her hoofs and the queen goes some distance looking at the hollowed dust. Kalidasa excels all other poets in similes. Each poet has some distinction or other. There is a saying: "Upama Kalidasasya" (For similes Kalidasa-Kalidasa excels in similes). It is in the context of Sudhaksina following Nandini that the poet brings in the simile of the queen following the cow like the Smrtis following the Vedas.
Apamsulanam dhuri kirtaniya
-Raghuvamsam, 2. 2
"Pamsu" means dust. As Nandini goes grazing, dust is raised. "Khura" is hoof. "Khuranyasa" means placing of the hoof and "pavitra pamsum" the sacred dust.
The dust raised by the cow is particularly sacred. It sanctifies any place. Such is the case even with the dust raised by an ordinary cow, not to speak of the so sacred Nandini, Kamadhenu's daughter. Sudhaksina is a woman of spotless character - there is not a speck of dust on it - and such a woman has now cow dust on her. "Apamsu" means free of dust and refers to Sudhaksina of unblemished character. She goes step by step along the hollowed path following the dust raised by the hoofs of the cow. How? Like the Smrtis composed by the sages that follow the Vedas - "Sruterivartham Smrtiranvagacchat".
"Anvagacchat" = (she) followed. Here the upamana (that with which a comparison is made) for the cow is Sruti or the Vedas. The "hoof steps" of the cow are to be taken as the meaning of the Vedas.
So Sudhaksina followed in the "hoof steps" of Nandini like the Smrtis following the meaning of the Vedas. Also, like the Smrtis not going in the entire way with the Vedas, she did not go all the distance with the cow. The idea is that the Smrtis do not repeat all that is said in the Vedas. They are "notes from memory", but they truthfully follow the Vedas in their meaning. They do not, of course, represent all thousands of mantras of the scriptures but, all the same, they tell us how to make use of the Vedas.
"Sudhaksina with her pure antah-karana followed her husband and, without deviating even a little, walked along the path of the dust raised by Nandini's hoofs". Having said so much, Kalidasa thought he must bring in a good simile for Sudhaksina following the cow dust and it occurred to him in a flash: "Like the Smrtis following faithfully the meaning of the Vedas. "
The upamana is always superior to the upameya. If a face is compared to the lotus or the moon, the lotus or the moon must be more beautiful than the face. Here Sudhaksina, of matchless purity of character, following her husband Dilipa is likened to the Smrtis closely following the Vedas. No better authority is needed to support the view that the Smrtis are in accord with the Vedas.
For a general background, please see here