“Is not My word like a fire?” says the Lord, “And like a hammer that breaks the rock in pieces?” (Jeremiah 23:29). 
Billy Graham once said-
“Time and time again in my ministry, I have quoted a Bible verse in a sermon, sometimes without planning to do so in advance, only to have someone tell me afterward it was that verse which the Holy Spirit used to bring conviction of faith to him.” 
Knowing God’s Word is essential-
– for any person who wants to lead others to Jesus Christ.
Anyone who shares the Gospel needs to use the Word of God. 
When Philip met the Ethiopian in the desert, the Bible tells us, “Then Philip opened his mouth, and beginning at this Scripture, preached Jesus to him” (Acts 8:35).
What if Philip had not been a student of Scripture when the Ethiopian was looking for answers?  
He would have had to say, “I don’t know…that’s a good question. Uh, can I get back to you?”  
Philip was well-versed in what the Scripture taught. 
That is why we are told in 2 Timothy 2:15, “Be diligent to present yourself approved to God, a worker who does not need to be ashamed, rightly dividing the word of truth.”  
I am not saying we need to have the answer to every question.
But I am saying that we need to study and prepare ourselves as effectively as possible.