三折肱 A Thrice Broken Arm
八戒道：「現在看榜的官員在此。」說不了，只見那幾個太監、校尉朝上禮拜道：「孫老爺，今日我王有緣，天遣老爺下降。是必大展經綸手，微施三折肱，治得我王病愈，江山有分，社稷平分也。」八戒道：「现在看榜的官员在此。」说不了，只见那几个太监、校尉朝上礼拜道：「孙老爷，今日我王有缘，天遣老爷下降。是必大展经纶手，微施三折肱，治得我王病愈，江山有分，社稷平分也。」
逐句解 Line by line
Eight Rules said, "The officers who watch the notice are standing right here."
現在 is 'at this very moment'. His whole case now rests on witnesses rather than on being believed.
Before he had finished, the eunuchs and guardsmen made their bows toward the seat of honour: "Old Master Sun, our king is in luck today, that Heaven should send Your Honour down to us.
了 keeps its full tone liǎo in 說不了, to finish speaking — the verb, not the little particle that marks a completed action. They use 孫老爺 exactly as Eight Rules coached them to a few passages back.
"Assuredly you will unfold your statesman's hand and apply a little of the thrice-broken arm, and cure our king of his sickness — and half the realm shall fall to your share, the altars of state divided in two."
Two instances of 分 in the last clause, read differently. 有分 is fèn, a share falling due to somebody — 康熙字典 files that reading separately at 刀部二畫 under 扶問切, 汾去聲, glossing it 名分也 and 分位也, and the sealed chapters read the same compound that way. 平分 is the primary reading fēn, 府文切, 音餴, glossed 別也 — to divide. The machine gives fēn at both.
三折肱 is the chapter's own title arriving in the text, and it arrives once only. The phrase comes from an old saying that a man who has broken his arm three times has learned enough to set one — expertise bought by injury. The officials produce it as flattery.
They also hand Pilgrim the whole imposture in a single bow. He stole a notice and told his brother he was buying vinegar; the court's own servants are now addressing him by the title he was coached into, crediting him with a statesman's hand, and quoting the price.
有分 and 平分 sit four characters apart and read differently — a share falling due, and an estate cut in two. The sentence offers both at once, which is more than the proclamation did.