Only by daybreak the elder was nodding and swaying in the saddle.

搖樁打盹, yáo zhuāng dǎ dǔn, is dozing in the saddle and swaying as you go — 樁, zhuāng, is a post driven into the ground, so the picture is of a loose fence-stake rocking. Anyone who has nodded off on a late train will know the movement.

The Pilgrim saw it and called out: "Master, you are not up to it—how can a man who has left the household be so worn out?

不濟, bú jì, "not up to it, no good" — blunt, and said to a man who has been tied to a pillar all day. 出家人, one who has left the household. 辛苦, xīn kǔ, worn out.

"I, old Sun, could go a thousand nights unsleeping and never know the least fatigue.

The boast is meant kindly, which somehow makes it worse. 千夜不眠, a thousand nights without sleep, and 不曉得些困倦, "wouldn't know the least tiredness," with the linking 得, de.

"Just dismount; do not let travellers on the road see you and laugh, but rest a while in a wind-sheltered, breath-gathering spot under the hillside, and then go on."

Then the practical advice, which turns out to be surprisingly technical. 藏風聚氣, cáng fēng jù qì, "storing wind and gathering breath," is a term straight out of Chinese siting lore — the practice English calls fengshui — for a spot that shelters from wind and holds good energy, which is what you look for when choosing a house or a grave. Wukong is picking a rest stop by the same criteria you would use to site a tomb. 藏 here is cáng, "to store," not the zàng of his master's name. 莫教走路的人看見笑你, don't let passers-by see you and laugh — the concern is entirely for the master's dignity.