Comparing Gospel with Gospel / Scripture with Scripture
Before any conclusion can be made about an event recorded in the gospels, all the gospels must be taken into account.
For example, in Matthew, Mark, and John, one with Jesus takes his sword and cuts off the ear of one of the high priest's servants. Anyone reading these accounts would think the man thereafter lived life with one ear. But in Luke's account (Luke 22:50,51), we read that Jesus healed the man's ear.
All 4 gospels must be read to harmonize all events recorded there.
We can see how God's giving us of the gospels is also instructing us to compare other Scriptures (gospel account with gospel account) before arriving at our conclusion.
And so it is with any teaching of the Bible. We must diligently compare Scripture with all other Scripture (1 Corinthians 2:13) in order to find truth and have a conclusion harmonious with the whole of the Bible.