The subject of the letter was the catechesis of Pope Francis during his General Audience on 11 August 2021, in which he referred in the context of the theology of Saint Paul (cf. Gal 3,19.21-22) to the Jewish Torah. On 24 August 2021, Rabbi David Sandmel, Chair of the International Jewish Committee for Interreligious Consultations (New York), wrote a similar letter to Cardinal Koch.
After consulting with His Holiness Pope Francis, on 3 September 2021 Cardinal Koch responded both to Rabbi Arussi and Rabbi Sandmel:
Letter to Rabbi Arussi
Letter to Rabbi Sandmel
(See also: Philip A. Cunningham, Pope Francis' Catecheses on the Letter to the Galatians)