JUD 1:3

3 Chaverim, although I was very eager to write to you an iggeret hakodesh concerning the Geulah [(Redemption)] we share, it suddenly became necessary to write you an urgent appeal to fight for the Emunah [(Faith, the Emunah of the true Dat HaYehudit)], which was once for all time handed over and transmitted to the Kedoshim.