Landau was born in Opatów, Poland, to a family that traced its lineage back to Rashi, and attended yeshiva at Ludmir and Brody.

While in Yampol, he attempted to mediate between Jacob Emden and Jonathan Eybeschütz in a debate—"The Emden-Eybeschütz Controversy"—that "had disrupted Jewish communal life for many years".

He had a controversy on this subject with Baruch Jeiteles (Phinehas Hananiah Argosi di Silva), who, under the title of Ha-Oreb, published (Vienna, 1795) Landau's letter to him and his own rejoinder.

This collection was esteemed by rabbis and scholars, both for its logic and for its independence with regard to the rulings of other Acharonim as well as its simultaneous adherence to the writings of the Rishonim.

[3] In his sefer Derushei HaTzlach,[4] Landau argued that the Zohar can not be considered reliable, since it only came into the hands of the Jewish people many hundreds of years after Rashbi's death, and thus lacks an unbroken mesorah as to its authenticity, among other reasons.

He particularly singled out Hartwig Wessely for criticism after the publication of the latter's Divrei Shalom V'emes, which advocated abandoning the traditional Jewish educational system, in favor of one with an emphasis on secular studies.

In one response, he writes "...In this generation of ours [people] have abandoned God’s Torah and the source of living waters–the two Talmuds, Bavli and Yerushalmi–to dig for themselves broken cisterns.

Besides the specific debate over the status of Jonathan Eybeschuetz, Jacob Emden expressed strong disagreement with Landau's approach, advocating instead for a far more aggressive anti Sabbatean strategy.