They still did not understand the scripture may be translated “but even then they did not understand what the scripture meant when it said that…” or “… did not really understand what the words of the scripture meant which said that…” or “… did not know how to understand the words of the scripture, He must rise from death.”

Which said that he must rise from death is more literally “that he must rise from (the) dead.” John does not indicate what scripture he has in mind. Although the word scripture commonly refers to a single passage of the Old Testament (note 19.36-37), in the present passage the term is better taken as a reference to the Old Testament as a whole. The word must indicates a necessity based on the divine will and purpose.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .