Imam Khomeini (ra) was among the world's top spiritual leaders to influence boycotts against Israel, starting in 1967. With the victory of the Islamic Revolution of Iran under his leadership in 1979, Iran cut all ties with Israel.
After the 6-day war had been launched between Israel and Arab countries, Imam Khomeini issued a message wherein he called any relationship with Israel ‘haram’ or religiously prohibited. This message was in a way the main initiative that led to pervasive ‘Boycott Israel’ campaigns.
The message was issued on June 07, 1967.
(A memoirs and statement by the supreme leader)