Why is Israel like an olive?
R. Yohanan said:
Why is Israel said to be like an olive? Because as the olive will not yield its oil unless it is crushed, so Israel do not return to the right way unless they are crushed by affliction. (B. Men 53b and En Yaakov, ad loc.)
We read in Exod. R. 36:1
“A leafy olive tree, fair with goodly fruit” (Jer. 11:16). Olives, while still on the tree, are marked for shriveling, after which they are knocked down and brought up to a roof, where they are left to dry; then they are placed in a grinding mill, where they are ground; their pulp is then tied up in a hempen bale, upon which heavy stones are placed. Only after all that do olives yield their oil. So, too Israel. The nations of the earth knock them down, drive them from place to place, imprison them, put chains around their necks, and post soldiers all around them. Only then do Israel resolve on repentance, and the Holy One responds to them.