Ewald was born to Jewish parents in Maroldsweisach, Bavaria,[2] and baptized at Basel when about 23 years of age.
He proselytised assiduously among the Jews in Algiers, Tunis, Tripoli, and other large towns in North Africa until 1841 or 1842, when he accompanied as chaplain Bishop Alexander to Jerusalem.
He was largely instrumental in founding in 1853 the Wanderers' Home in London, an asylum for "doubting Jews and needy proselytes."
In addition to reports on his missionary labors in North Africa and Jerusalem, he published a German translation of Avodah Zarah (1856).
The University of Erlangen, of which Ewald was a graduate, on the publication of this work, conferred upon him the diploma of a Doctor of Philosophy, and Archbishop Tait conferred upon him, in 1872, the degree of Bachelor of Divinity in consideration "of his uprightness of life, sound doctrine, and purity of morals; of his proficiency in the study of divinity, of Hebrew and Oriental languages and literature; and also of his missionary labors and eminent services in the promotion of Christianity among the Jews.