At confirmation the bishop gives a little slap to the cheek. What is the origin and meaning of that slap?
Before the reform of the celebration of the sacraments, bishops would routinely give each confirmand a symbolic tap on the cheek. As confirmation strengthens the Christian to witness to Christ and to spread and defend the Christian faith (cf. canon 879, Code of Canon Law) the cheek tap was a symbol of the hardship that the Christian would face in his Christian life. Confirmation gave him the grace he would need to draw on to overcome the hardship.
The symbolic tap is no longer part of the confirmation ritual but the grace of confirmation still strengthens the confirmand and enables him to be faithful to Christ.