But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto Me… – Acts 1:8

If you are a disciple of Christ, you are not to look into the times and the seasons which the Father hath put in His own power; you are to receive the Spirit of God, and then there is something for you to be. Did you expect me to say that then there is something for you to do? Well, there is a great deal for you to do; but the text says, “Ye shall be witnesses”; not “Ye shall act as witnesses” only, but “Ye shall be witnesses.” Every true Christian should, in his own proper person, be a witness for his Lord. “Here I stand,” says he, “myself a proof of what my Lord can do. I, His servant, saved by Him, and renewed by Him, washed in His blood, it is I who, while I live, whether I speak or not, am a monument of His love, a trophy of His grace.” “Ye shall be Witnesses unto Me.”

Dear friends, we are to be witnesses of what Christ has done. If we have seen Christ, if we believe in Christ, let us tell it honestly. These apostles had a great deal to tell. They had been with Christ in private; they had seen His miracles; they had heard His choicest and more secret words; they had to go and bear witness to it all. And you, who have been let into the secrets of Christ, you who have communed with Him more closely than others, you have much to tell. Tell it all, for whatever He has said to you in the closet you are to proclaim upon the housetop. You are to witness what you have seen, and tasted, and handled, concerning your Lord. You are to witness to what He has revealed, to make known to others the doctrine that He preached, or taught by His apostles. Mind that you do not tell any other. You are not sent to be “an original thinker”, to make up a gospel as you go along; you are a witness, that is all, a re-teller of Christ’s truth, and you miss the end of your life unless you perpetually witness, and witness, and witness to what you know of Him, and to what you have learnt from Him. Let this be your prayer and your resolve-

“Give me Thy strength, O God of power!
Then let winds blow, or thunders roar,
Thy faithful witness will I be:
‘Tis fixed: I can do all through Thee.”

You are to witness to what you have experienced concerning Christ. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2330.cfm