St Matthew 12 includes some of those robust exchanges with the Pharisees, involving some name calling on the part of Our Lord (ye brood of vipers, etc) that tends to be somehow bypassed by the WWJD/tolerance and niceness crowd. Today's section of the text sets the scene, with a discussion (and demonstration) of what it is lawful to do on the sabbath:
In illo tempore abiit Jesus per sata sabbato: discipuli autem ejus esurientes cœperunt vellere spicas, et manducare. 2 Pharisæi autem videntes, dixerunt ei: Ecce discipuli tui faciunt quod non licet facere sabbatis. 3 At ille dixit eis: Non legistis quid fecerit David, quando esuriit, et qui cum eo erant: 4 quomodo intravit in domum Dei, et panes propositionis comedit, quos non licebat ei edere, neque his qui cum eo erant, nisi solis sacerdotibus? 5 aut non legistis in lege quia sabbatis sacerdotes in templo sabbatum violant, et sine crimine sunt? 6 Dico autem vobis, quia templo major est hic. 7 Si autem sciretis, quid est: Misericordiam volo, et non sacrificium: numquam condemnassetis innocentes: 8 dominus enim est Filius hominis etiam sabbati. 9 Et cum inde transisset, venit in synagogam eorum. 10 Et ecce homo manum habens aridam, et interrogabant eum, dicentes: Si licet sabbatis curare? ut accusarent eum. 11 Ipse autem dixit illis: Quis erit ex vobis homo, qui habeat ovem unam, et si ceciderit hæc sabbatis in foveam, nonne tenebit et levabit eam? 12 Quanto magis melior est homo ove? itaque licet sabbatis benefacere. 13 Tunc ait homini: Extende manum tuam. Et extendit, et restituta est sanitati sicut altera.14 Exeuntes autem pharisæi, consilium faciebant adversus eum, quomodo perderent eum. 15 Jesus autem sciens recessit inde: et secuti sunt eum multi, et curavit eos omnes: 16 et præcepit eis ne manifestum eum facerent. 17 Ut adimpleretur quod dictum est per Isaiam prophetam, dicentem: 18 Ecce puer meus, quem elegi, dilectus meus, in quo bene complacuit animæ meæ. Ponam spiritum meum super eum,et judicium gentibus nuntiabit. 19 Non contendet, neque clamabit, neque audiet aliquis in plateis vocem ejus: 20 arundinem quassatam non confringet, et linum fumigans non extinguet, donec ejiciat ad victoriam judicium: 21 et in nomine ejus gentes sperabunt.
And in English:
At that time Jesus went through the corn on the sabbath: and his disciples being hungry, began to pluck the ears, and to eat.  And the Pharisees seeing them, said to him: Behold thy disciples do that which is not lawful to do on the sabbath days.  But he said to them: Have you not read what David did when he was hungry, and they that were with him:  How he entered into the house of God, and did eat the loaves of proposition, which it was not lawful for him to eat, nor for them that were with him, but for the priests only?  Or have ye not read in the law, that on the sabbath days the priests in the temple break the sabbath, and are without blame?  But I tell you that there is here a greater than the temple.  And if you knew what this meaneth: I will have mercy, and not sacrifice: you would never have condemned the innocent.  For the Son of man is Lord even of the sabbath.  And when he had passed from thence, he came into their synagogues.  And behold there was a man who had a withered hand, and they asked him, saying: Is it lawful to heal on the sabbath days? that they might accuse him. But he said to them: What man shall there be among you, that hath one sheep: and if the same fall into a pit on the sabbath day, will he not take hold on it and lift it up?  How much better is a man than a sheep? Therefore it is lawful to do a good deed on the sabbath days.  Then he saith to the man: Stretch forth thy hand; and he stretched it forth, and it was restored to health even as the other.  And the Pharisees going out made a consultation against him, how they might destroy him.  But Jesus knowing it, retired from thence: and many followed him, and he healed them all.  And he charged them that they should not make him known.  That it might be fulfilled which was spoken by Isaias the prophet, saying:  Behold my servant whom I have chosen, my beloved in whom my soul hath been well pleased. I will put my spirit upon him, and he shall shew judgment to the Gentiles.  He shall not contend, nor cry out, neither shall any man hear his voice in the streets.  The bruised reed he shall not break: and smoking flax he shall not extinguish: till he send forth judgment unto victory.  And in his name the Gentiles shall hope.
In reflecting on this passage, St John Chrysostom first adds the summary of the teaching from this incident provided in St Mark's Gospel:
After this He mentions another reason likewise; For the Son of man, says He, is Lord of the Sabbath day; Matthew 12:8 speaking it of Himself. But Mark relates Him to have said this of our common nature also; for He said, The Sabbath was made for man, not man for the Sabbath. Mark 2:27
The point is that the sabbath is meant to benefit us, not hurt:
For indeed the Sabbath did at the first confer many and great benefits; for instance, it made them gentle towards those of their household, and humane; it taught them God's providence and the creation, as Ezekiel says; Ezekiel 20:12 it trained them by degrees to abstain from wickedness, and disposed them to regard the things of the Spirit.
For because they could not have borne it, if when He was giving the law for the Sabbath, He had said, Do your good works on the Sabbath, but do not the works which are evil, therefore He restrained them from all alike for, You must do nothing at all, says He: and not even so were they kept in order. But He Himself, in the very act of giving the law of the Sabbath, did even therein darkly signify that He will have them refrain from the evil works only, by the saying, You must do no work, except what shall be done for your life. And in the temple too all went on, and with more diligence and double toil. Numbers 28:9-10 Thus even by the very shadow He was secretly opening unto them the truth.
St John goes on to argue that far from abolishing the sabbath rest, Christ enhanced it in ways consistent with the law of grace:
Did Christ then, it will be said, repeal a thing so highly profitable? Far from it; nay, He greatly enhanced it. For it was time for them to be trained in all things by the higher rules, and it was unnecessary that his hands should be bound, who was freed from wickedness, winged for all good works; or that men should hereby learn that God made all things; or that they should so be made gentle, who are called to imitate God's own love to mankind (for He says, Be merciful, as your Heavenly Father); Luke 6:36 or that they should make one day a festival, who are commanded to keep a feast all their life long; (For let us keep the feast, it is said, not with old leaven, neither with leaven of malice and wickedness; but with unleavened bread of sincerity and truth); 1 Corinthians 5:8 as neither need they stand by an ark and a golden altar, who have the very Lord of all for their inmate, and in all things hold communion with Him; by prayer, and by oblation, and by scriptures, and by almsgiving, and by having Him within them. Lo now, why is any Sabbath required, by him who is always keeping the feast, whose conversation is in Heaven?
Let us keep the feast then continually, and do no evil thing; for this is a feast: and let our spiritual things be made intense, while our earthly things give place: and let us rest a spiritual rest, refraining our hands from covetousness; withdrawing our body from our superfluous and unprofitable toils, from such as the people of the Hebrews did of old endure in Egypt.