It is a phrase which is very easily used in preaching. It normally takes the form of an exhortation. “You need to have faith in the finished work of Christ”, or “You must place your faith in the cross” are two ways it is expressed. We so very easily accept such statements without “batting an eye-lid”. But are they really accurate? I would suggest not.
The relentless call of Scripture is that we need to have faith in Christ. Paul reviewing his ministry in Ephesus says that I have declared to both Jews and Greeks that they must turn to God in repentance and have faith in our Lord Jesus (Acts 20:21). Our faith is to be in Jesus Christ the Lord who once died on the cross to take away our sins. Our faith is not to be in an event, but in a person. When we come by faith to the person of Christ we come into union with Him. We come into the blessing of all that He is and all that He has done for us. Therefore everything that He is as the One who once died for our sins and is now alive and risen and is there in heaven for us is made good to us and for us.
Let me be careful to emphasise here that I believe that the message of the cross is central to our faith. Without the proclamation of Christ and Him crucified there is no gospel message. But we must be careful and biblical in our expressions. We are not called to believe in the cross. We are called to believe in the Christ who gave Himself on the cross for us.