Paul is distressed with the Galatians as they are abandoning the true essence of the gospel. He is in anguish because their salvation is compromised. He preaches that Christ was crucified, using the past tense “crucified” to show that Christ's death didn't simply happen in the past – but it is something that happened with dynamic relevance and power for the present. The single requirement for this glorious salvation is faith. The single key to experiencing the power of the cross for your own soul is to believe it.