One of my favorite subjects to read about and discuss is apparent contradictions in the Bible. Some are as easily explained as texts being taken out of context, while others take more work.
I am going to start a series that addresses these alleged contradictions in order to show that they are actually not. If you have any suggestions, send them in and I will write about them (or link to an article that does).
This question was addressed to The Gospel Coalition:
The Gospel of Mark begins, “As it is written in Isaiah the prophet, ‘Behold I send my messenger before your face, who will prepare your way.'” Only problem: that quote is from Malachi, not Isaiah. Did Mark just fumble the ball here? How do we make sense of this apparent error in Scripture?
The apparent contradiction is found in Mark 1:1-3. As the question states, it appears that Mark is citing Isaiah on a piece of scripture that was actually written by Malachi.
Rikk E. Watts goes a great job of explaining why this is not a contradiction and how it was a literary technique that Mark used over and over in his Gospel. It is a good article and well worth a read.