"They want me to give them a sign" or "Many of you want me to give you a sign." The information about what kind of sign they wanted can be made explicit as in the UDB. (See: [[rc://en/ta/man/translate/figs-explicit]])
## no sign will be given to it ##
"God will not give them a sign" (See: [[rc://en/ta/man/translate/figs-activepassive]])
## the sign of Jonah ##
This could be translated as "what happened to Jonah" or "the miracle that God did for Jonah" (UDB).
## For just as Jonah became a sign...so too ##
This means that Jesus will serve as a sign from God for the the Jews of that day in exactly the same way as Jonah served as a sign from God to the people of Nineveh.