Rabbi Matisyahu Salomon, a spiritual counselor at America’s largest yeshivas who spearheaded a crusade to warn observant Jews of the risks posed by the internet, died on Jan. 2 in Lakewood, NY. He was 86.

Rabbi Salomon was dean of students during his three decades at Beth Medrash Govaha, a religious school in Lakewood with an enrollment of more than 9,000 students, where he guided thousands of young men in ethical and pious conduct.

A decade ago, he led a campaign to warn observant Jews that new technologies were threatening observance of the laws, traditions and principles that are the backbone of their Ultra-Orthodox faith, beguiling pious Jews with videos, images and temporal content that would distract them from their family life, daily religious obligations, and pursuits like Torah study. In 2012, a rally in support of the concept packed Citi Field with 20,000 believers.