He is Rabbi Emeritus of Congregation Kehilath Jeshurun on the Upper East Side of Manhattan, where he served most his entire rabbinic career (1958–2015) He was also principal of the Ramaz School from 1966 through 2015.
[5] Lookstein started first grade at the Ramaz School in 1937, the year it was established by his father, by then senior rabbi of Congregation Kehilath Jeshurun.
[6][7] After receiving his rabbinic ordination from Rabbi Isaac Elchanan Theological Seminary in 1958, he was offered pulpits in Detroit and at the Sephardic Temple in Cedarhurst, New York.
The Rabbinical Council of America (RCA), the primary American modern-Orthodox rabbinic association, initially took exception to his presence, stating that "participation in a prayer service held in the sanctuary of a church is prohibited" and adding: "Any member of the RCA who attends such a service does so in contravention of this policy and should not be perceived as representing the organization in any capacity.
[18] In July 2016, Lookstein accepted the invitation of Ivanka Trump, a member of his congregation, to offer the opening invocation at the 2016 Republican National Convention (RNC).
After the invitation was made public, many Kehilath Jeshurun congregants, as well as Ramaz alumni, signed a petition requesting that Lookstein refrain from appearing at the RNC, condemning Trump's "racist, misogynistic rhetoric".
His prepared remarks, which Lookstein also sent out, included the following benediction: [22] [23] Almighty God: We know that we are living in very dangerous times, when all of these blessings are threatened from without, by forces of terror and unimaginable brutality, and from within, by those who sow the seeds of bigotry, hatred, and violence, putting our lives and our way of life at risk.In the aftermath, some argued that the pressure put on Lookstein to withdraw was counterproductive, inferring, from the content of his prepared remarks, a subtle rebuke to then-nominee Trump.