Acts 1:8 defines the believer's identity as witness before it defines any task: "But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me." A witness is not an evangelist by profession or a theologian by training. A witness is someone who reports what they have personally seen and heard. The legal background of the word martyres makes this concrete — in a court, a witness does not argue, persuade, or perform. They testify to firsthand knowledge. That is the job.
First Peter 3:15 adds the posture that makes witnessing work: "Be ready always to give an answer to every man that asketh you a reason of the hope that is in you with meekness and fear." The word for "answer" is apologia — a legal defense, a carefully considered response. This is not cold-call persuasion. It is a response to someone who notices something in you and asks. The prerequisite is a life that raises questions.
Acts 4:20 records Peter and John before the Sanhedrin — the most hostile possible audience — and their response is not argumentative: "For we cannot but speak the things which we have seen and heard." The word "cannot" is the key. They are not claiming courage. They are claiming compulsion. When you have genuinely seen something, silence becomes the thing that requires effort. That kind of witnessing is not a duty you force yourself toward. It is an overflow.
Commentary is from a charismatic Protestant perspective, drawing on KJV text and public-domain sources including Spurgeon, Andrew Murray, and Matthew Henry.