Gobhilagrihyasutra 3.4.31

3.4.31

goyuktaṃ ratham upasaṃkramya pakṣasī kūbarabāhū vā 'bhimṛśed vanaspate vīḍvaṅgo hi bhūyā iti.

(The student then) should approach a chariot yoked with oxen, and should touch its two side-pieces or the two arms of the chariot-pole with (the verse), 'O tree, may thy limbs be strong' (ibid. 16).