机锋话头是什么

问五台路。曰由孟县至代州峨口。秘魔岩僧清一。善持戒。问几远。曰二千零。天晴取雪煮粥。指釜问。南海有这个么。曰无。吃什么。曰水。釜雪溶水。丐指曰是什么。公无语默然不知所对。　

宣化偈曰：
南海这个有也无。所吃何物水缘熟。
复问水是何物也。公难应对语默如。

Asking the piercing question, "What Is It?"

The Master then asked about the road to Wu T'ai Mountain. Wen Chi told him that from Meng Hsien, he would pass through Tai Chou and then O K'ou (Lofty Mouth), where there was a bhikshu in Pi Mo (Hidden Demons) Cavern named Ch'ing Yi (Primal Purity). He was one who well upheld the moral precepts. "How far is Wu T'ai Mountain from here?" asked the Master. "Two thousand li," said Wen Chi. At daybreak, Wen Chi took some snow to make gruel. Pointing to it in the pot, he asked, "Do you have this in Nan Hai?" "No," replied the Master. "Then what do you drink there?" "Water." By that time, the snow in the pot had melted into water. The beggar pointed to the pot again and said, "Well, then, what is this?" The Master was speechless and did not know what to answer.

The verse says:
"Do you have this in Nan Hai, friend, or is it not to be found there?"
"If not, then what is there to drink?" he pressed, as the water's cause ripened. 
"I wish to ask you once again, just what is this water?"
Although the Master should have answered, he couldn't say a word.