Madhvacharya has quoted the Balittha Sukta (Rig Veda 1.141.1-5) at the end of his commentary on the Brhadaranyaka Upanishad
to assert himself to be an incarnation of Vayu:
balittha tad vapusedhayi darsatam devasya bhargah sahaso yato ajani |
yadimupahvarate sadhate matir-rtasya dhena anayanta sasrutah || 1 ||
prkso vapuh pitumannitya asaye dvitiyamasaptasivasu matrsu |
trtiyamasya vrsabhasya dohase dasapramatim janayantayosanah || 2 ||
niryadim budhnanmahisasya varpasa isanasah savasa krantasurayah |
yadimanupradivo madhva adhave guhasantam matarisva mathayati || 3 ||
prayatpituh paramanniyateparyaprksudho virudho dansu rohati |
ubhayasya janusam yadinvata adidyabistho abhavadhdhrna sucih || 4 ||
adinmatrravisadyasva sucirahimsyamana urviya vivavrdhe |
anuyatpurva aruhastanajuvoni navyasisva varasu dhavate || 5 ||
After quoting the above Suktam, Madhvacharya goes on to comments on it as follows:
The three forms of Vayu which have the auspicious qualities of 'krida' (sporting), etc., are well described in the Vedic texts -- as being of the essence of strength (bala), full of pious knowledge (jnana). They protect the world, impart divine knowledge and are extremely holy and sacred. All the three forms appeared in the world per the desire of the Supreme Being. Just like the main (mula) form, these forms also are full of strength and knowledge (with no diminution during incarnation). The first form of Hanuman takes the words of Shri Rama (to Sita). It also teaches the precious and auspicious knowledge from Mula Ramayana to its disciples, for their salvation. The second form, as Bhima, is the main destroyer (of evil forces of the Kauravas and others). The third form of Madhva has composed this bhasya (Brhadaranyaka) to please the Supreme Lord - Shri Hari.
The word 'hanu' means knowledge and hence, Hanuman is refered as 'Mati' in the Sukta by Madhvacharya. The words "rtasya dhena anayanta sasrutah" mean that Hanuman carried the message (dhena) of Shri Rama (rta) who is always Eternal or Changeless and who is the essence of Truth, to Sita.'rtasya dhena anayanta sasrutah' can also mean that he taught the immutable and eternal truths such as the Mula Ramayana (the original Ramayana composed of a hundred crore slokas, given by Lord Hayagriva to Brahma) to his disciples for their salvation. "prkso vapuh" describes the Bhima incarnation. 'bhima' has the same meaning as "a saye saptasivasu matrsu." 'Bhima' is "one who has all knowledge of the sacred texts" (sastras). The expansion in support of this is given as 'bhrtah mah yena sa bhimah' -- bhrtah (supported, repository of); mah, from the same root as pra-mah, (sources) of valid knowledge, or pramanas, yena sah (from whom). 'ma-tr' means all the valid sastra texts. These are the four Vedas -- Rig, Yajur, Sama and Atharva, along with itihasa, purana and pancaratra. 'saye' means "well versed in." Bhima is well versed in all the seven sources of valid knowledge given above. The words 'trtiyamasya vrsabhasya dohase' describe Shri Madhva. The word 'madhva' means "the author of 'va' (sastras) which give 'madhu' (bliss). Similarly 'tirtha' means the same as 'va'. Thus 'Ananda Tirtha' and 'Madhva' mean the same thing. It is stated that anyone who understands correctly the reference to the three forms of Vayu described in this Sukta, will understand all the Vedas correctly and will secure valid knowledge (tattva-jnana) with the blessings of Vayu.
The Balittha Sukta has also been quoted by Madhvacharya in his other works. These works are as follows:
Shri Mahabharata Tatparya Nirnaya
Commentaries on the Taittiriya Upanishad, Aitareya Upanishad and the Chandogya Upanishad.
Vishnu Tattva Vinirnaya
Tantra Sara Sangraha
Note that this interpretation of the Balittha Sukta is limited to the Madhvas only as neither traditional commentators on the Vedas such as Sayanacharya nor modern translators of the Rig-Veda such as H.H. Wilson, believe the Balittha Sukta to be a hymn dedicated to Vayu. The Sukta is generally regarded to be dedicated to Agni.
Note: Personally, I disagree with Madhvacharya's interpretation (and assertion of himself being Vayu's avatara) of the Balittha Sukta. Therefore, this answer doesn't represent my views.