This refers to God's word, which they believed. Alternate translation: "God's word that you heard and the truth that you believed" (See: [[rc://en/ta/man/translate/figs-explicit]])
Being alert to danger is spoken of as waking up. See how you translated "wake up" on [Revelation 3:2](../03/02.md). Alternate translation: "If you are not alert" or "If you are not careful" (See: [[rc://en/ta/man/translate/figs-metaphor]])