Why was it necessary to put out Patroclos' pyre with wine in the Iliad?

Question

In Book XXIII of the Iliad, after Patroclos' body has been burnt, Achillês tells the Greeks to put out the pyre with wine:

Now the people were all gathering round Agamemnon. They made such noise and uproar that Achillês sat up and said:
"Atreidês, and you other princes, you must first quench the pyre with wine wherever the flames have touched. Then let us gather the bones of Patroclos Menoitidês, and be careful to find the right ones. [...]"
They did his bidding at once. First they quenched the pyre with wine wherever it had burnt and the ashes were deep; then weeping they gathered the bones of their gentle companion, and laid them covered with fat in a golden urn, which they wrapt up in fine linen and put away safely in the hut.
_{(translation by W.H.D. Rouse, 1938)}

Why was it necessary to put it out using wine? What's the significance of quenching the pyre with wine instead of water?

Answer 1

Achilles is performing a prolonged libation to the gods, as happened in prior paragraphs to get the fire going (source of Rouse's translation).

But the pyre would not burn, and Achillês did not know what to do. At last he stood well away from the smouldering heap, and prayed to North Wind and West Wind promising them good sacrifices; many a libation he poured from his golden goblet, praying them to come and make the wood quickly catch fire, to burn the bodies.

The gods indeed intervene to ensure that the fire glows hot.

Her message given, away she flew, and the Winds rose with a devil of a noise and drove the clouds in a riot before them. They swooped upon the sea and raised the billows under their whistling blasts; they reached the Trojan coast and fell on the pyre till the flames roared again. All night long they beat upon the fire together blowing and whistling; all night long stood Achillês holding his goblet, and dipt into the golden mixer, and poured the wine on the ground, till the place was soaked, calling upon the soul of unhappy Patroclos. As a father laments while he burns the bones of his own son, newly wedded and now dead, to the grief of his bereaved parents, so Achillês lamented as he burnt the bones of Patroclos, stumbling up and down beside the pyre with sobbings and groanings.

Because these flames were granted by the gods, Achilles continued to make offerings to them in thanks for their divine favor (admittedly, that's my inference rather than directly stated in the text).