Śatapatha Brāhmaṇa ("of a hundred paths") 1.3.4

They should be green (fresh); for that is (what constitutes) their living element, by that they are vigorous, by that possessed of strength: for this reason they should be green.

The middle stick he lays down first (on the west side of the fire), with the text (Vâg. S. II, 3), 'May the Gandharva Visvâvasu lay thee around for the security of the All! Thou art a fence to the sacrificer, thou (art) Agni, invoked and worthy of invocation!'

He then lays down the southern one, with the text (ib.), 'Thou art Indra's arm for the security of the All! Thou art a fence to the sacrificer; thou Agni, invoked and worthy of invocation!'

He then lays down the northern one, with the text (ib.), 'May Mitra-Varuna lay thee around in the north with firm law for the security of the All! Thou art a fence to the sacrificer, thou Agni, invoked and worthy of invocation!' They are indeed Agnis, and for that reason he says, 'Agni, invoked and worthy of invocation!'

Thereupon he puts on (the fire) a samidh (kindling-stick). He first touches with it the middle enclosing-stick: thereby he first kindles those (three Agnis). After that he puts it on the fire: thereby he kindles the visible fire.

He puts it on, with the gâyatrî stanza (Vâg. S. II, 4), 'Thee, O Sage, who callest (the gods) to the feast, we will kindle so as to shine brilliantly; thee, O Agni, mighty at the sacrifice!' He thereby kindles the gâyatrî; the gâyatrî, when kindled, kindles the other metres; and the metres, when kindled, carry the sacrifice to the gods.

By the second kindling-stick (samidh), which he now puts on, he kindles the spring; the spring, when kindled, kindles the other seasons; and the seasons, when kindled, cause living beings to be produced and the plants to ripen. He puts it on, with the formula (Vâg. S. II, 5), 'A kindler (samidh) art thou!' for the spring is indeed a kindler.

When he has put it on, he murmurs (ib.), 'May the sun guard thee from the east against any imprecation!' for the enclosing-sticks serve for protection on all (the other three) sides; and thereby he makes the sun the protector on the east side, fearing 'lest the evil spirits, the Rakshas, should rush in from the east:' for the sun is the repeller of the evil spirits, the Rakshas.

By that third kindling-stick, then, which he puts on at the after-offerings, he kindles the officiating priest (brâhmana); and he, the priest, when kindled, carries the sacrifice to the gods.

He now returns to the altar covered (with sacrificial grass). Having taken two stalks of grass, he lays them down across (the barhis or grass covering, with the tops to the north), with the formula (Vâg. S. II, 5), 'Savitri's arms are ye!' The prastara bunch is indeed the top-knot (of the sacrifice); and he now lays down these two crosswise as its eye-brows: thereby these two (represent) the transverse eye-brows. The prastara, further, (represents) the kshatra (or military class); and the other barhis the vis (or, the common Âryan people);--(and the two stalks he puts down between them) for the sake of separating (vidhriti) the kshatra and the vis: for this reason he lays them down crosswise; and for this reason these two (stalks) are called vidhriti.

On them he spreads the prastara, with the formula (Vâg. S. II, 5), 'I spread thee, soft as wool, pleasant to sit upon for the gods!' When he says 'thee, soft as wool,' he means to say 'agreeable to the gods;' and by 'pleasant to sit upon for the gods' he means to say 'forming a good seat for the gods.'

He presses it down (with his left hand), with the text (ib.), 'May the Vasus, the Rudras, the Âdityas sit on thee!' These three, that is, the Vasus, the Rudras, and the Âdityas, namely, are (classes of) gods; and these, he means to say, are to sit down on it. While it is still being held down with his left hand,--

He seizes the guhû with his right, fearing 'lest the evil spirits, the Rakshas, should enter there in the meantime;' for the officiating priest (brâhmana) is the repeller of the Rakshas: therefore, while it (the prastara) is still being held down with his left hand,--

He seizes the guhû, with the text (Vâg. S. II, 6), 'Fond of butter art thou, Guhû by name!' for fond of butter indeed it is, and Guhû by name;--'Sit down here with the favourite resort (or dainty) on the favourite seat!' The upabhrit (he takes), with the formula (ib.), 'Fond of butter art thou, Upabhrit by name!' for fond of butter indeed it is, and Upabhrit by name;--'Sit down here with the favourite resort on the favourite seat!' The dhruvâ (he takes) with 'Fond of butter art thou, Dhruvâ by name!' for fond of butter indeed it is, and Dhruvâ by name;--'Sit down here with the favourite resort on the favourite seat!' What other sacrificial food there is, (he puts down on the prastara), with the formula, 'With the favourite resort sit down on the favourite seat!'

He lays the guhû down on (the prastara), and the other spoons down below, (viz. on the barhis, north of the guhû, and so as not to touch it or one another); for the guhû assuredly is the kshatra, and the other spoons (sruk) are the vis: he thereby makes the kshatra superior to the vis. Hence the people here serve, from a lower position, the Kshatriya seated above them: for this reason he places the guhû upon (the prastara) and the other spoons down below it.

He touches the offerings, with the text (Vâg. S. II, 6), 'Safely they have sat down,' for safely indeed they sat down;--'in the lap (yoni) of divine truth!' for the sacrifice is indeed the lap of divine truth, and in the sacrifice they sat down;--'Protect these, O Vishnu! protect the sacrifice! protect the lord of sacrifice!' thereby he refers to the sacrificer;--'Protect me, the leader of the sacrifice!' thereby he does not exclude himself either from the sacrifice. Vishnu, assuredly, is the sacrifice: hence it is to the sacrifice that he makes all that over for protection. This is the reason why he says, 'Protect these, O Vishnu!'