There are alleged discrepancies in the Bible and usually, they appear because they are not taken in proper context, viewed at the time of writing or perspective from the eyewitnesses standpoint. Obviously, anyone investigating the inerrancy of the Bible should fully investigate the validity of the Scriptures however at some point individuals must ask themselves if their motive is to investigate or find the most minute error in order to disprove the text in order to excuse their faith in the text.
A classic example of Scripture that on the surface appears to contradict other Scripture are the books of Matthew and Mark and Luke and the instructions of Jesus sending the disciples out into the mission field. The two verses from the New American Standard are:
9 Do not acquire gold, or silver, or copper for your money belts, 10 or a bag for your journey, or even two coats, or sandals, or a staff; for the worker is worthy of his support. Matthew 10:9-10
8 and He instructed them that they should take nothing for their journey, except a mere staff-no bread, no bag, no money in their belt- 9 but to wear sandals; and He added, "Do not put on two tunics." Mark 6:8-9
3 And He said to them, "Take nothing for your journey, neither a staff, nor a bag, nor bread, nor money; and do not even have two tunics apiece. Luke 9:3
The two concessions of a staff and sandals are unique to Mark. Both are forbidden in Matthew 10:9-10, and the staff is forbidden in Luke 9:3. Matthew used ktaomai (“to procure, acquire”), instead of airō (“to take”); so the disciples were not to acquire additional staffs or sandals – but to use the ones they already had. Mark and Luke both use airō, “to take or carry along.” But Luke says, “Take nothing for the journey – no staff (rhabdon)" presumably no additional staff; while Mark says, “Take nothing for the journey except (Mark 6:5) a staff (rhabdon),” presumably the one already in use. Each writer stressed a different aspect of Jesus’ instructions (p. 128, emphasis original).
So the apparent contradiction is resolved. Or the three passages do not add up to a contradiction if they are read in their historical and textual contexts and according to their proper sense.
However, it is understandable that some readers may not be satisfied with the explanation in that excerpt. So the following comment on the three passages is worth taking to heart:
Only if one has a very legal mind is there a significant difference . . . Jesus normally speaks in the hyperbole of a wisdom teacher, not the legal precision of a Pharisee . . . These passages are also another reminder to us that we do not have all of the answers . . . these passages call us not to lose the forest for the trees. Jesus called his missionaries to travel simply, without the normal provisions for a journey. They had to depend on God for their support.” (Kaiser, et al., pp. 423-24)
Notice how that team of scholars mentions “hyperbole.” That is an acceptable literary Scriptural device, which is an intentional exaggeration to draw attention to the main point. For example, Jesus uses a hyperbole when he says that we should not pull a speck out of our bother’s eye, while we have a big beam or plank in our eye (Matt. 7:3). Can we literally have a beam or plank in our eye? Can we rightly say, “There’s an error in Scripture because no one can literally have a beam or plank in his eye!” However, the attitude behind the “gotcha” misses the literary technique of hyperbole.
The same is true of the mustard seed. Is it the smallest seed (Matt. 13:32; Mark 4:31)? The question misses the point. Jesus was using hyperbole to encourage his followers. Even if our faith is very small – the smallest it can be – it can grow to benefit those around us. Plus, historically the mustard seed “was the smallest seed used by farmers and gardeners there and at that time”. So the hyperbole is resolved by the historical context – as if it's our job to “fix” hyperboles. Nonetheless, time resolves the puzzle.