1 Timothy 1:3
3As I urged you when I was going into Macedonia, stay at Ephesus that you might command certain men not to teach a different doctrine,
Timothy is to remain and command certain men not to teach a different doctrine. The deposit is the apostolic gospel, not a private hobby of the teacher.
Arminians hear both authority and responsibility: the church must refuse additions and replacements, and teachers can actually swerve. Grace enables Timothy to stay at his post; it does not make the charge optional.
Paul arms Timothy with a charge, not a suggestion. Remaining at Ephesus is apostolic strategy for a church in danger of novelty.
God guards the gospel through appointed means—a clear command, a faithful deputy, and the refusal of rival teaching. The church is not a marketplace of doctrines; it lives by the one gospel entrusted to the apostle.