Klein was ordained deacon on May 17, 1927, by Bishop
Ethelbert Talbot, and priest on June 24, 1928, by Bishop
Sheldon Munson Griswold. He served as assistant priest at the
Church of St Mary the Virgin in
New York City between 1930 and 1934, and curate at
Grace Church in
Newark, New Jersey. In 1937, he became vicar of St Augustine's Church in
Norristown, Pennsylvania, and also accepted the post of lecturer at the
Philadelphia Divinity School. In 1938, he became chairman of the graduate department of the Philadelphia Divinity School, where he remained till 1942. Between 1942 and 1943, he served as rector of St Barnabas' Church in
Haddington, Philadelphia. He also served as a naval chaplain during
WWII between 1943 and 1946. After the war, he joined the staff of the
Anglican Bishop of Jerusalem and became a
canon of the
Cathedral chapter of
St George's Cathedral in
Jerusalem in 1948. He resigned the post in 1950 to become a professor of Old Testament Literature and Languages at
Seabury-Western Theological Seminary. He also served as the seminary's assistant dean between 1952 and 1959. In 1959, he was elected Dean of
Nashotah House, and retained the post till 1963. ==Episcopacy==