Learn, my brethren, what is the meaning of the sign of the Cross. When we put our hand on [our] head, it reveals God who is in the sky. When we put it over [our] navel, it reveals that he descended to earth and became incarnate. When we put [our] hand on the right breast, it reveals that he is just and eternal and that he will place the just on his right hand. And when we put it on [our] left side, it reveals that he will judge all the nations and they will stand on his left side and he will put them into hell.
The holy Cross, my brethren, is the wellspring of the whole earth. The holy Cross blesses the entire world, all that is divine and holy in the churches. The Cross blesses the Divine Liturgy and every service. The Cross blesses the saints. The Cross blesses and strengthens baptism. The Cross blesses couples. The Cross chases away demons who flee like lightning. The Cross is a bright weapon, and whoever makes the sign of the Cross is illuminated and is blessed. It is like a double-edged sword to which the demons don’t draw near to urge people to commit sin.
Wherever a person sets out to travel, he should first make the sign of the Cross and say the prayer: “Lord Jesus Christ.” Whether you go to the fair or to the field, or to the vineyard, or when you eat bread or fruit, or drink wine or water, when you go to sleep, worship God. Make the sign of the Cross over your body and then lie down to sleep. You will then sleep and will rise in the morning strong and happy. So, my brethren, you have understood and now know.
– From Father Kosmas the Apostle of the Poor: The Life of St. Kosmas Aitolos Together With an English Translation of His Teaching and Letters by Nomikos Michael Vaporis, Brookline, MA: Holy Cross Orthodox Press, 1977.