Rabbi Abba son of Kahana said, “David’s generation were all righteous, but because there were informers among them, they fell in battle...Ahab’s generation were idolaters, but because there were no informers, they went to battle and were victorious.”
Jerusalem Talmud, Peah 1:1.

Jerusalem is the city that joins all the tribes together as one. When the Jewish people come together as one, nothing can destroy Jerusalem. And only when there is love and caring between them is the destruction and our exile healed.

When a father sees his children working together with love, he is prepared to give them anything.

Yes, love for one another means also to care enough to encourage the other to do mitzvahs and learn Torah.

But first comes the love.

See Likutei Sichot, vol. 30, pg. 221.