攔住大仙 Intercepting the Immortal
那虎力大仙欠身拱手，辭了國王，徑下樓來。行者向前攔住道：「先生那裡去？」大仙道：「登壇祈雨。」行者道：「你也忒自重了，更不讓我遠鄉之僧。那虎力大仙欠身拱手，辞了国王，径下楼来。行者向前拦住道：「先生那里去？」大仙道：「登坛祈雨。」行者道：「你也忒自重了，更不让我远乡之僧。
逐句解 Line by line
Tiger-Power the Immortal rose with a slight bow and cupped his hands, took his leave of the king, and came straight down from the tower.
那虎力大仙: 那 = nà. 欠身拱手 "half-rising, hands cupped" -- a courteous salute, done sitting down. 辭 "to take leave."
Pilgrim stepped forward, blocked his way, and said, “Sir, where are you off to?”
行者: 行 = xíng. 攔住 "to block the way." 那裡去: 那 = nǎ, the questioning reading -- "where are you off to?"
The immortal said, “To mount the altar and pray for rain.”
登壇祈雨 "to go up the altar and pray for rain."
Pilgrim said, “You are far too full of yourself, giving no way at all to me, a monk from a distant land.
忒自重: 重 = zhòng in 自重, to think a lot of yourself. 更不讓: 更 = gèng; the falling tone of 讓 pulls 不 to bú.
Wukong steps in front of Tiger-Power before he can reach the altar. What follows looks like a squabble about manners and is in fact the decisive manoeuvre of the contest.
His opening complaint -- you are far too full of yourself, giving no way to a monk from far off -- is mock-injured etiquette, the outsider claiming his turn. It puts the immortal on the back foot over something trivial, which is the ideal position from which to ask him for something important.