1 Thessalonians 5:8

But let us, since we are of the day, be sober, putting on the breastplate of faith and love; and for a helmet, the hope of salvation.

For extended comment on Paul's famed triad of "faith, hope and love," see under 1 Thessalonians 1:3, above. Amazingly, Paul here switched metaphors in the middle of a train of thought, a style characteristic of the blessed apostle and absolutely impossible of forgery or imitation. Only Paul could have done a thing like this. As Paul was familiar with military operations, it would appear that his mention of "watch and be sober" triggered the thought of an armed sentry; and, as the "armor of God" metaphor was a favorite of his, he immediately combined it with the prime virtues of faith, hope and love. The fullest development of the metaphor is in Ephesians 6:13ff.