But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth. Acts 1:8 (KJV)
A witness is someone who has personal knowledge or encounter with Christ Jesus and shares their faith to win souls for Christ. Every Christian has been called upon to witness for Jesus Christ. This is the will of God for every Christian because God is not willing that any soul should perish without getting the opportunity to be saved. You cannot be a good witness without the power of the Holy Spirit. The primary evidence that you have the power of the Holy Spirit is the speaking in tongues and prophesying, Acts 2:4. Dear beloved, if you have not yet received the power of the Holy Spirit, it is not too late for you. Desire the gift of the Holy Spirit and ask the Lord Jesus Christ to give it to you. Receive it by faith and pray fervently, and you will find yourself speaking in tongues. Read 1 Corinthians 14 to know how to exercise it and be a good witness for the Lord. Hallelujah! Be An Overcomer!