Not slothful - The word rendered “slothful” refers to those who are slow, idle, destitute of promptness of mind and activity; compare Matthew 25:16.
In business - τῇ σπουδῇ tē spoudē. This is the same word which in Romans 12:8 is rendered “diligence.” It properly denotes haste, intensity, ardor of mind; and hence, also it denotes industry, labor. The direction means that we should be diligently occupied in our proper employment. It does not refer to any particular occupation, but is used in general sense to denote all the labor which we may have to do; or is a direction to be faithful and industrious in the discharge of all our appropriate duties; compare Ecclesiastes 9:10. The tendency of the Christian religion is to promote industry:
(1) It teaches the value of time.
(2) Presents numerous and important things to be done.
(3) It inclines people to be conscientious in the improvement of each moment.
(4) And it takes away the mind from those pleasures and pursuits which generate and promote indolence.
The Lord Jesus was constantly employed in filling up the great duties of his life, and the effect of his religion has been to promote industry wherever it has spread both among nations and individuals. An idle man and a Christian are names which do not harmonize. Every Christian has enough to do to occupy all his time; and he whose life is spent in ease and in doing nothing, should doubt altogether his religion. God has assigned us much to accomplish; and he will hold us answerable for the faithful performance of it; compare John 5:17; John 9:4; 1 Thessalonians 4:11; 2Th 3:10, 2 Thessalonians 3:12. All that would be needful to transform the idle, and vicious, and wretched, into sober and useful people, would be to give to them the spirit of the Christian religion; see the example of Paul, Acts 20:34-35.
Fervent - This word is usually applied to water, or to metals so heated as to bubble, or boil. It hence is used to denote ardor, intensity, or as we express it, a glow, meaning intense zeal, Acts 18:25.
In Spirit - In your mind or heart. The expression is used to denote a mind filled with intense ardor in whatever it is engaged. It is supposed that Christians would first find appropriate objects for their labor, and then engage in them with intense ardor and zeal.
Serving - Regarding yourselves as the servants of the Lord. This direction is to be understood as connected with the preceding, and as growing out of it. They were to be diligent and fervid, and in doing so were to regard themselves as serving the Lord, or to do it in obedience to the command of God, and to promote his glory. The propriety of this caution may easily be seen.
(1) The tendency of worldly employments is to take off the affections from God.
(2) People are prone to forget God when deeply engaged in their worldly employments. It is proper to recall their attention to him.
(3) The right discharge of our duties in the various employments of life is to be regarded as serving God. He has arranged the order of things in this life to promote employment. He has made industry essential to happiness and success; and hence, to be industrious from proper motives is to be regarded as acceptable service of God.
(4) He has required that all such employments should be conducted with reference to his will and to his honor, 1 Corinthians 10:31; Ephesians 6:5; Colossians 3:17, Colossians 3:22-24; 1 Peter 4:11. The meaning of the whole verse is, that Christians should be industrious, should be ardently engaged in some lawful employment, and that they should pursue it with reference to the will of God, in obedience to his commands, and to his glory.