Cyril of Alexandria — as excerpted in the Catena Aurea on Luke 10:1-2

“An outline of this ordinance also was set forth in the words of Moses, who at the command of God chose out seventy, upon whom God poured out His Spirit. In the book of Numbers also it was written of the children of Israel, that they came to Elim, which is by interpretation “ascent,” and there were there twelve fountains of water, and seventy palm trees. (Numb. 33:9.) For when we fly to spiritual refreshment, we shall find twelve fountains, namely, the holy Apostles, from whom we imbibe the knowledge of salvation as from the well-springs of the Saviour; (Isai. 12:3.) and seventy palms, that is, those who were now appointed by Christ. For the palm is a tree of sound core, striking deep root and fruitful, always growing by the water side, yet at the same time putting forth its leaves upwards. It follows, And he sent them two and two.”