七弟兄 The Seven Sworn Brothers
羅剎道：「還未去。昨日到我這裡借扇子，我因他害孩兒之故，披掛了，掄寶劍出門，就砍那猢猻。他忍著疼，叫我做嫂嫂，說大王曾與他結義。」大聖道：「是五百年前曾拜為七弟兄。」罗刹道：「还未去。昨日到我这里借扇子，我因他害孩儿之故，披挂了，抡宝剑出门，就砍那猢狲。他忍着疼，叫我做嫂嫂，说大王曾与他结义。」大圣道：「是五百年前曾拜为七弟兄。」
逐句解 Line by line
The Rākṣasī said, "He has not gone yet. Yesterday he came here to borrow the fan, and because of his harming our child I put on my armour, swung out my precious sword and slashed at the ape."
還 is hái. 兒 in 孩兒, child, is the full ér.
"He bore the pain, called me sister-in-law, and said my lord had once sworn brotherhood with him."
忍著 takes the continuous zhe. Her account is accurate in every detail: the Great Sage did take the sword-cuts without hitting back, and he did claim the brotherhood, in the previous chapter.
The Great Sage said, "Five hundred years ago we did indeed bow together as seven sworn brothers."
為 is the copular wéi. And notice who is doing the confirming. The one fact everybody in these two chapters has been arguing about — was there really a sworn brotherhood — is settled here by a man wearing the face of the only person entitled to settle it.
The passage settles a question the whole story has turned on. The Great Sage claimed a sworn brotherhood at this door in the previous chapter and was refused; he claimed it again to the Bull King himself and got a pardon out of it. Here the Rākṣasī reports the claim as something a stranger asserted, and it is confirmed by somebody who is not the person entitled to confirm it. The truth arrives through the mouth of the impersonator.
The number is worth noting. 七弟兄, seven sworn brothers, reaches back to chapter three, where the Monkey King bound himself to six other demon kings of the mountains. Of that fellowship this chapter has produced exactly two members, on opposite sides of a quarrel about a fan, five centuries later.