1 Corinthians 14:37 “If any man think himself to be a prophet, or spiritual, let him acknowledge that the things that I write unto you are the commandments of the Lord.” 

If any man think himself to be a prophet, etc. - He who is really a spiritual man, under the influence of the Spirit of God, and capable of teaching the Divine will, he will acknowledge that what I now say is from the same Spirit; and that the things which I now write are the commandments of God, and must be obeyed on pain of his displeasure. 

1 Corinthians 14:38 “But if any man be ignorant, let him be ignorant.” 

But if any man be ignorant - If he affect to be so, or pretend that he is ignorant; let him be ignorant - let him be so at his peril. 

1 Corinthians 14:39 “Wherefore, brethren, covet to prophesy, and forbid not to speak with tongues.” 

Covet to prophesy - Let it be your endeavor and prayer to be able to teach the way of God to the ignorant; this is the most valuable, because the most useful gift of the Spirit. 

And forbid not to speak with tongues - Let every gift have its own place and operation; let none envy another; nor prevent him from doing that part of the work to which God, by giving the qualification, has evidently called him. 

1 Corinthians 14:40 “Let all things be done decently and in order.” 

Let all things be done decently - Ευσχημονως· In their proper forms; with becoming reverence; according to their dignity and importance, Every thing in the Church of God should be conducted with gravity and composure, suitable to the importance of the things, the infinite dignity of the object of worship, and the necessity of the souls in behalf of which those religious ordinances are instituted. 

And in order - Κατα ταξιν· Every thing in its place, every thing in its time, and every thing suitably. 

Let all things be done decently and in order, is a direction of infinite moment in all the concerns of religion, and of no small consequence in all the concerns of life. How much pain, confusion, and loss would be prevented, were this rule followed! There is scarcely an embarrassment in civil or domestic life that does not originate in a neglect of this precept. No business, trade, art, or science, can be carried on to any advantage or comfort, unless peculiar attention be paid to it. And as to religion, there can be absolutely none without it. Where decency and order are not observed in every part of the worship of God, no spiritual worship can be performed. The manner of doing a thing is always of as much consequence as the act itself. And often the act derives all its consequence and utility from the manner in which it is performed.