Do not extinguish the Spirit.
19 Quench not the Spirit. This metaphor is derived from the power and nature of the Spirit; for as it is the proper office of the Spirit to illuminate the understandings of men, and as he is on this account called our light, it is with propriety that we are said to quench him, when we make void his grace.
Spiritual joy in God can be constant; rejoice in Him and you have an everlasting feast, even when worldly troubles strike. Prayer without ceasing is the path to that joy. Thanksgiving in all things, even hardship, follows naturally when you pray, for you will always find matter to thank God for.
AI summary
Commenting on 1 Thessalonians 5:16-22
Prove all things,.... That are said by the prophets, all the doctrines which they deliver; hear them, though they have not the gift of tongues, and all desirable advantages; do not reject them on that account, and refuse to hear them, for so, many useful men may be laid aside, and the Spirit of God in them be quenched; try their gifts, and attend to...