Ex cathedra is a Latin phrase which means "from the chair." It refers to binding and infallible papal teachings which are promulgated by the pope when he officially teaches in his capacity of the universal shepherd of the Church a doctrine on a matter of faith or morals and addresses it to the entire world. The concept derives from Jesus.
In Matthew 23: 2-3 Jesus spoke of the authority of the Old Testament magisterium saying, "The scribes and the Pharisees have taken their seat on the chair [Gk. cathedras] of Moses. Therefore, do and observe whatsoever they tell you, but do not follow their example. For they preach what they do not practice." Since Jesus recognized the authority of the Old Testament magisterium when it spoke ex cathedra (with the authority of Moses), we recognize that the New Testament magisterium of the Church, which speaks with the authority not of Moses but of Jesus Christ himself (Mt 10:40, 16:18-19, 18:18; Lk 10:16; 2 Cor 5:18-20), possesses a binding, infallible teaching office which is guaranteed by Christ (Mt 28:20; Jn 14:16, 26, 16:13).