John Calvin Commentary 1 Corinthians 16:13

"Watch ye, stand fast in the faith, quit you like men, be strong." — 1 Corinthians 16:13 (ASV)

Watch ye. A short exhortation, but of great weight. He exhorts them to watch, so that Satan may not oppress them, finding them off their guard. For as the warfare is incessant, the watching must also be incessant.

Now, spiritual watchfulness is this: when, free and disentangled from earthly cares, we meditate on the things of God. For just as the body is weighed down by surfeiting and drunkenness, (Luke 21:34), so that it is fit for nothing, so too the cares and lusts of the world, idleness or carelessness, are like a spiritual surfeiting that overpowers the mind.

The second thing is that they persevere in the faith, or that they hold fast the faith, so as to stand firm, because that is the foundation on which we rest. It is certain, however, that he points out the means of perseverance—by resting on God with a firm faith.

In the third exhortation, which is very similar in nature, he stirs them up to manly fortitude. And, since we are naturally weak, he exhorts them fourthly to strengthen themselves, or gather strength. For where we translate it as be strong, Paul uses only one word, which is equivalent to strengthen yourselves.