For David, after he had served his own generation by the will of God, fell on sleep, and was laid unto his fathers, and saw corruption. – Acts 13:36

Though our citizenship is in heaven, yet as we live on earth, we should seek to serve our generation while we pass as pilgrims to the better country. What, then, is it for a man to serve his own generation?

It is not to drop into the habits, customs, and ideas of the generation in which we live. People talk nowadays about Zeitgeist, a German expression which need frighten nobody; and one of the papers says, “Spurgeon does not know whether there is such a thing.” Well, whether he knows anything about Zeitgeist or not, he is not to serve this generation by yielding to any of its notions or ideas which are contrary to the Word of the Lord. The gospel of Jesus Christ is not only for one generation, it is for all generations. It is the faith which needed to be only “once for all delivered to the saints”…It cannot change because it has been given of God and is therefore perfect; to change it would be to make it imperfect. It cannot change because it has been given to answer for ever the same purpose, namely, to save sinners from going down to the pit, and to fit them for going to heaven. That man serves his generation best who is not caught by every new current of opinion, but stands firmly by the truth of God, which is a solid, immovable rock…

Is it not a grand thing to build up, from the beginning of life to the end of it, the same gospel? But to set up opinions to knock them down again, as though they were ninepins, is a poor business for any servant of Christ. David did not, in that way serve his own generation; he was the master of his age, and not its slave. I would urge every Christian man to rise to his true dignity and be a blessing to those amongst whom he lives, as David was. Christ “hath made us kings and priests unto God His Father”; it is not meet that we should cringe before the spirit of the age or lick the dust whereon “advanced thinkers” have chosen to tread. Beloved, see to this and learn the distinction between serving your own generation and being a slave to it. ~ C.H. Spurgeon

https://www.blueletterbible.org/comm/spurgeon_charles/sermons/2243.cfm