Karma Kanda of Vedas, Vedangas are treated as Apara Vidhya and Upanishads are treated as Para Vidhya, since the former only give us rebirth and Upanishads provide us Knowledge of Brahman, through which we can attain Moksha. This is what Mundaka Upanishad 1.1.4-5 says. But I would like to know if the Karma Kanda of Vedas, especially Brahmanas themselves anywhere say they won't help in achieving liberation.
There's no verse in the Karma Kanda that specifically says that moksha can't be obtained through yajnas, but the Karma Kanda lists the fruits of each yajna, and none of them reward moksha; they reward material things, and the results are temporary. So from that it's known that the Karma Kanda doesn't directly reward moksha.
But however, it indirectly leads to moksha, because someone who reads the karma kanda realizes the fruits of yajnas are temporary, then reads the vedanta kanda, realizes that moksha is eternal, and strives to achieve moksha.
Ramanujacharya says this in his commentary on the Brahma Sutras:
The purport of the entire Sûtra then is as follows: 'Since the fruit of works known through the earlier part of the Mîmâmsâ is limited and non-permanent, and since the fruit of the knowledge of Brahman--which knowledge is to be reached through the latter part of the Mîmâmsâ--is unlimited and permanent; for this reason Brahman is to be known, after the knowledge of works has previously taken place.'
[The study of the Vedas] has for its result the accurate determination of the nature of those things and their different modes. Through this study the student ascertains the character of the injunctions of work which form part of the Veda, and observes that all work leads only to non-permanent results; and as, on the other hand, he immediately becomes aware that the Upanishad sections--which form part of the Veda which he has apprehended through reading--refer to an infinite and permanent result, viz. immortality, he applies himself to the study of the Sârîraka-Mîmâmsâ, which consists in a systematic discussion of the Vedânta-texts, and has for its result the accurate determination of their sense.
However, there are explicit statements in the Upanishads (Jnana kanda) that say that the results of yajnas are temporary, while moksha is eternal.
That the fruit of mere works is transitory, while the result of the knowledge of Brahman is something permanent, the Vedanta-texts declare in many places.
And the fruits of the Yajnas themselves are mentioned in the actual mantras of the Samhitas, and then the Brahmanas section elaborates on how to perform the Yajnas to achieve those fruits. Like for example, from the Taittiriya Samhita: "He who desires prosperity should offer a white (beast) to Vayu." And also: "He who desires cattle should offer one of a triplet to Soma and Pusan."