Charles Spurgeon Commentary Luke 11:29-30

"And when the multitudes were gathering together unto him, he began to say, This generation is an evil generation: it seeketh after a sign; and there shall no sign be given to it but the sign of Jonah. For even as Jonah became a sign unto the Ninevites, so shall also the Son of man be to this generation." — Luke 11:29-30 (ASV)

And there shall no sign be given it, but the sign of Jonas the prophet. For as Jonas was a sign unto the Ninevites, so shall also the Son of man be to this generation.

Jonah rose, as it were, from the dead, for he was buried in the deep, in the belly of the whale; and Christ was buried in Joseph's tomb, yet he came back from the grave on the third day.