Some think Matthew chronicled in Aramaic the sayings and deeds of Jesus as he traveled with Him. Nobody knows for sure; this might be the hypothetical “Q” document that stands behind and is a common source for the Synoptic Gospels: Matthew, Mark and Luke. But Matthew is a chronicler and ultimately writes his Gospel in Greek. And watching Jesus, his mind spun back to the Old Testament book of Isaiah and he saw in what Jesus did a fulfillment of Isaiah’s prophecy, which he quotes in verse 20,
“A bruised reed shall he not break, and the smoking flax shall he not quench.” (Isaiah 42:3)
Nobody knows what the bruised reed is. Whether it was a musical instrument made from the reeds or just the reed growing, it really doesn’t matter. The point is that it was bruised almost to the point of breaking, its usefulness or its life about gone; and the Scripture says, finding that condition, it is Jesus’ nature not to break it.
The smoking flax referred to the wick on the edge of a Hebrew lamp, almost out, just smoking, with no fire left in it. Matthew applies it to Jesus’ treatment of those in human need: when the spark is almost gone, when there is little if any light left, when it is just smoking, He won’t quench it.