竭力修持 Strive And Do Not Slacken
吾等奉佛旨差來助汝，汝當竭力修持，勿得須臾怠惰。」三藏叩齒叩頭，受身受命。吾等奉佛旨差来助汝，汝当竭力修持，勿得须臾怠惰。」三藏叩齿叩头，受身受命。
逐句解 Line by line
"We were dispatched by the Buddha's command to help you. You must strive with all your strength in your practice, and not slacken for a moment."
Being told the work is nearly complete turns out to be the setup for being told not to relax. 差 is chāi, to dispatch on commission, the same reading as at the four Vajras' own announcements a few passages back. 勿得 takes 得 at dé, the "must not" frame that this edition rules with 只得, 休得 and 方得. 須臾 is a Buddhist term for the smallest useful division of time.
Tripitaka clicked his teeth and knocked his head, and received the charge with body and life.
叩齒 is a Daoist ritual gesture, the teeth struck together to summon the attention of the spirits, and it sits here beside the Buddhist prostration of 叩頭 with no sense of incongruity at all. 受身受命 doubles the verb: he receives it in his body and in his allotted span.
The instruction is short and it is a warning rather than a congratulation. 汝當竭力修持，勿得須臾怠惰 — strive with all your strength, do not slacken for a moment. Being told the work is nearly complete turns out to be the setup for being told not to relax.
叩齒叩頭 puts a Daoist ritual gesture and a Buddhist prostration in the same four characters, and the novel sees nothing to remark on. 受身受命 doubles the receiving: in the body and in the allotted span, which is as close as Tripitaka comes to an answer.