Meaning of the Cross

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.

By Saint Kosmas the Aitolos

Let no man therefore be ashamed of the honored symbols of our salvation, and of the chiefest of all good things, whereby we even live, and whereby we are; but as a crown, so let us bear about the cross of Christ. Yea, for by it all things are wrought, that are wrought among us. When one is  new-born, the cross is there; or to be nourished with the mystical food, or to be ordained, or to do anything else, everywhere our symbol of victory is present. Therefore both on house and walls, and windows, and upon our forehead, and upon our mind, we inscribe it with much care. For of the salvation wrought for us, and of our common freedom, and of the goodness or our Lord, this is the sign...not merely by the fingers ought one engrave it, but before this by the purpose of the heart with much faith. And if in this way thou hast marked it on thy face, none of the unclean spirits will be able to stand near thee, seeing the blade whereby he received his wound, seeing the sword which gave him his mortal stroke. 

By Saint john Chrysostom
(Nicene and Post Nicene Fathers, P. Shaff, ed., vol x, pp 335-36)