伸著光頭 A Bald Head Offered
行者叉手向前，笑道：「嫂嫂切莫多言。老孫伸著光頭，任尊意砍上多少，但沒氣力便罷。是必借扇子用用。」行者叉手向前，笑道：「嫂嫂切莫多言。老孙伸着光头，任尊意砍上多少，但没气力便罢。是必借扇子用用。」
逐句解 Line by line
Pilgrim folded his hands before him, stepped up and said with a laugh, 'Sister-in-law, say no more about it.'
叉手 is a formal gesture of respect, the hands folded one over the other at the chest. He answers a threat of decapitation with a courtesy, which is the whole of his method in this scene.
'Old Sun will put out his bald head. Strike as often as your honour pleases — only when you have no strength left, let us have done.'
伸著 marks the action as ongoing, zhe. 光頭, a bare head, is what a monk has; the joke is that his is also unbreakable. 任尊意, "as your honoured intention wills," keeps the politeness elaborate while inviting her to have a go.
'But the fan I must borrow, and use.'
是必, "it must be, without fail." Seven characters, and the whole negotiation is restated as a condition he has no intention of dropping.
Pilgrim accepts the ordeal with a folded-hands bow and a laugh, and the courtesy never slips: 嫂嫂, sister-in-law, and 任尊意, as your honour pleases. He is being invited to submit to decapitation and he answers in the manner of a man declining a second cup of tea.
The offer he makes is precisely calibrated. Strike as often as you like — 但沒氣力便罷, only when you have no strength left, let us stop. He is not proposing to endure a fixed number of blows but to outlast her arm, which turns the test from one of pain into one of her stamina.
And then the condition, in seven characters: but the fan I must borrow. Everything before it is concession and politeness; this is the thing he will not move on, and he states it last so that it is the sentence she is left holding.