'Watch you, stand fast in the faith, quit you like men, be strong. Let all that you do be done in love.'
He pleads with them to be both men of strength and men of love. Strong against both what is within and without that would challenge their faith and their lives, and loving to all who are within. They are to keep alert and watchful against all spiritual dangers and in readiness for Christ's coming (1 Corinthians 15:58), they are to stand firm, they are to behave as true men in the face of battle, they are to be strong.
‘Watch, (be alert, be vigilant).' This word was regularly used by Jesus of what our attitude should be to His coming. It may specifically mean that here, while at the same time indicating the need to be vigilant about maintaining purity of doctrine and avoiding being led astray.
‘Stand fast in the faith.' This is another exhortation which is constantly repeated elsewhere (compare 1 Corinthians 15:58 and 1 Corinthians 15:1-2). They are to stand firm against the Enemy, holding true to the faith, and themselves being strong in faith (compare Ephesians 6:10-18).
‘Quit you like men.' They are to show by their behaviour that they are truly strong. Such an order as this might well be given before a battle, and Paul is aware of the battles that lie ahead for the churches. Even the weakest of them is to be like a mighty man in the face of troubles that might arise (see Romans 5:1-5).
‘Be strong.' This reinforces the previous phrases. They are to be strong, strong in the Lord and in the strength of His might (Ephesians 6:10). In watching, in standing firm, and in battle they are to be strong with that inner strength that comes from Christ and that never yields against the Enemy and his forces. Psalms 31:24 may well be in mind here.
‘Let all that you do be done in love.' But lest any misinterpret his words he now stresses again the importance of Christian love. They are not to be hard with each other, but loving and tender. They are to show the love of chapter 13 towards each other.