Even after expulsion, the Jews did not stop intriguing against the Muslims. After the Hudaibiya pact with the Quraish, the Jews of Khyber entered into conspiracy with some of the tribes to attack Madina. The Holy Prophet anticipated the move of the Jews and marched with a force to Khyber. The Jews were overpowered.
"When a person dies, his works end, except for three: ongoing charity, knowledge that is benefited from, and a righteous child who prays for him."
Prophet Mohammed (PBUH)
"The best of what a man leaves behind are three: a righteous child who supplicates for him, ongoing charity the reward of which reaches him, and knowledge that is acted upon after him."
Sunan Ibn Mājah
"Every day two angels come down from Heaven and one of them says, 'O Allah! Compensate every person who spends in Your Cause,' and the other (angel) says, 'O Allah! Destroy every miser.'"
Sahih Bukhari