Jesus is recorded as sending his disciples out to do good works. Mark and Luke seem to disagree on whether Jesus forbade or permitted them to carry a staff. Here's Mark 6:8:
And here's Luke 9:3:
This would be a clear contradiction if it were not for the presence of a third passage, Matthew 10:9-10:
This passage from Matthew seems to suggest that Jesus was really telling them not to purchase anything new for their journey, but rather to go as they were. This would be consistent with Mark's account - they could take any staff they already had. Although this solves the problem for Matthew, it does not solve the problem for Luke, who doesn't say "don't acquire". He says "don't take".
However, I suppose that "take" itself can sometimes mean "acquire", and I wonder if this is true in the original Greek as well. The Apologetics Press (link below) argues that it is, and that Luke and Mark used the word in two different ways. Still, the general problem with infallibilism is the number of times you're forced to make excuses like this.