Why is having Christ as all important for salvation?

The doctrine of Christ as all emphasizes that salvation is entirely dependent on Christ's work and person. Believers must see Him as their only hope and source for acceptance before God. This is evident in the idea of the birthright discussed in the sermon, where Jacob represents those who know they must have Christ. If Christ is not all in a believer's salvation—meaning that no work or action on their part is necessary for justification—they are left without hope. Christ being all signifies that every aspect of salvation comes from Him, not depending on any works or righteousness of their own, reinforcing the sovereign grace through which they are saved.