The Seventy Disciples and Apostles of our Lord Jesus Christ are those Whom our Saviour chose in addition to the Twelve and sent forth unto the work of preaching. With the passage of time, others were added to their number by the Holy Apostles, who, with the accompaniment and assistance of the Seventy, were preaching the Gospel of Christ in various lands. Although their number eventually exceeded seventy, they were all nonetheless referred to as "of the Seventy" out of reverence for the number of Apostles which the Lord chose.
The divine Apostle and Evangelist Luke describes the calling and the sending forth of the Seventy as follows in his Holy Gospel (Luke 10:1-16): "After these things the Lord appointed another seventy disciples, and sent them two and two before His face into every city and place, whither He Himself would come. Therefore said He unto them, the harvest is great, but the labourers are few: pray ye therefore the Lord of the harvest, that He send forth labourers into His harvest. Go then: behold, I send you forth as lambs in the midst of wolves. Carry neither purse, nor bag, nor sandals: and greet no man on the way. And into whatsoever house ye enter first say, Peace be on this house. And if the son of peace be there, your peace shall rest upon it; if not, it shall turn to you again. And in the same house remain, eating and drinking such things as they give: for the labourer is worthy of his hire. Go not from house to house. And into whatsoever city you enter, and they receive you, eat such things as are set before you; And heal the sick that are therein, and say unto them, The Kingdom of God is come nigh unto you. But into whatsoever city ye enter, and they receive you not, go your ways out into the streets of the same, and say, Even the very dust of your city, which cleaveeth on us, we do wipe off against you: notwithstanding know ye this, that the Kingdom of God is come nigh unto you. But I say unto you, that it shall be more tolerable in that day for Sodom, than for that city. Woe unto thee, Chorazin! woe unto thee, Bethsaida! for if the mighty works had been done in Tyre and Sidon, which have been done in you, they had a great while ago repented, sitting in sackcloth and ashes. But it shall be more tolerable for Tyre and Sidon at the judgment, than for you. And thou, Capernaum, which art exalted to heaven, shalt be brought down to hades. He that heareth you heareth Me; and he that despiseth you despiseth Me; and he that despiseth Me despiseth Him that sent Me."
After the Passion, Resurrection, and Ascension of our Lord, and after Pentecost, on which all the Apostles and men and women disciples of Christ, together with the Most Holy Theotokos (some 120 in number), were gathered in the upper chamber, they received the grace of the All-holy Spirit and went forth throughout the ends of the world, everywhere preaching and teaching the Gospel of Christ, and leading to the true Faith the peoples who were sunk in the darkness of impiety and idolatry.