Not to shed any type of doubt on the Word of God but, why are all teachings taken from various verses throughout the Bible and not just from one place?
Good question and the scriptures have already answered that question for you. Isaiah 28:9 Whom shall he teach knowledge? and whom shall he make to understand doctrine? them that are weaned from the milk, and drawn from the breasts. 28:10 For precept must be upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little: In other words God knew exactly what He was doing when He had the Bible written. He knew in His infinite wisdom that this form not only made it necessary for us to dig to find His truths but that we would be exposed to His far deeper truths by making us see all of His Word as a whole.
This is why Paul told Timothy: 2nd Timothy 2:15 Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth. You can’t Rightly Divide if you don’t take the whole. Otherwise the division would be unequal.