Today at the Ascension Mass, our priest recounted how Tradition holds that Christ made the sign of the cross over Mary and the Apostles before he ascended into Heaven. "He lifted up His hands and blessed them" is interpreted as Christ raising his hands over the Apostles and then making the sign of the cross over them. This belief is affirmed by the Church Fathers (e.g. Saint Jerome).
The sign of the cross is of Apostolic origin and it remains in the liturgy and life of the Holy Church of Christ. Father Arthur Tonne provides us with examples:
i. The sign of the cross in some form or other is made about 54 times during Holy Mass.
ii. It is used frequently in the Divine Office or daily prayer of the priest.
iii. It is used in all blessings bestowed by bishop and priest.
iv. It is used in all the sacraments: 14 times in Baptism; 17 times in Extreme Unction. Yes, even in the semi-darkness of the confessional the priest makes the sign of the cross over you.
v. It is used in everything blessed for the service of God—altars, linens, holy water, etc.