Generally, we make it only before the Gospel. Maybe it’s worth doing outside Mass as well?
The holy Gospel according to Matthew, Mark, Luke or John – is said before the reading of the Gospel by the priest. Glory to you O Lord – we reply making three small signs of the cross with the thumb: on the forehead, the lips and the heart. What does this gesture mean?
The cross is a sign of our faith. It is always a profession: yes, I belong to Christ. It is also an expression of a certain commitment: I want to be worthy of the honourable name of Christian. In this context we can look at the triple sign of the cross. The forehead, the head, is for us the seat of thought. The sign of the cross on the forehead professes: I want Christ to be in my mind. Tracing it on the lips I say: I want to courageously profess Him. Repeating over the heart I profess that I also want Christ to be in my heart.
Christ? It is done before reading the Gospel. It seems justifiable in this context to add: when we make this sign on the forehead I want my thoughts to be permeated by the Good News announced by Him; I want His law to become the law by which I weigh up what is good and what is evil; I want to think as Christ thinks. When I make this sign on the lips, I express being prepared to proclaim the Good News and to respond in every matter according to the spirit of Christ’s Gospel. When I make it over the heart, I express the desire that Christ’s law of love was also my law and my love.
However, it is worth realising that the same sign – making a cross with the thumb – is done on the page of the Gospel to be read from the Lectionary (or book of Gospels). It’s like a request of the priest to always treat the Good News as sacred; not to distort it, not to twist it, not to use it as a stick to beat other believes or a club for sinners. This gesture is also used in celebrating the sacraments of Confirmation and Anointing of the Sick. Also, twice in the rite of baptism. First before the sacrament, first by the priest and then by the parents and godparents on the forehead of the child. Later after baptism, when the priest doing it on the child’s forehead with a finger dipped in holy oil he wishes that the newly baptised have “a share with Christ, priest, prophet and King for eternal life”. This brings us to yet another association: the threefold making of the sign the of cross with the thumb before the Gospel, can be understood as “setting up the guard”, “an echo of the seal”; as a request for the Son of God that He would protect us with His grace. When I do it, I ask: that Christ watch over my thoughts, may He guard my mouth and let Him protect my heart from evil; may I never be seduced by the temptations of the world but may I always be faithful to my thoughts, words and my (flowing from the heart) activities for the Gospel of Christ.