Albert Barnes on Matthew 12:20

A bruised reed, etc. The reed is an emblem of feebleness, as well as change, Mt 11:7. A bruised, broken reed, is an emblem of the poor and oppressed. It means that he would not oppress the feeble and poor, as victorious warriors and conquerors did. It is also an expressive emblem of the soul, broken and contrite on account of sin, weeping and mourning for transgression. He will not break it. That is, he will not be haughty, unforgiving, and cruel. He will heal it, pardon it, and give it strength.

Smoking flax. This refers to the wick of a lamp when the oil is exhausted--the dying, flickering flame and smoke that hang over it. It is an emblem, also, of feebleness and infirmity. He would not farther oppress it, and extinguish it. He would not be like the Jews, proud and overbearing, and trampling down the poor. It is expressive, also, of the languishing graces of the people of God. He will not treat them harshly or unkindly, but will cherish the feeble flame, minister the oil of grace, and kindle it into a blaze.

Till he send forth judgment unto victory. Judgment here means truth --the truth of God, the gospel. It shall be victorious. It shall not be vanquished. Though not such a conqueror as the Jews expected, ye he shall conquer. Though mild and retiring, yet his scheme shall be victorious.