The average evangelical sees the New Covenant as a lowered the bar of the law of God. He sees the OT God as a stickler for the rules, but the nice, gentle Jesus of the NT lets sin slide because He's a lot less uptight. The reality is that God has not lowered the standard. Not one bit.
We are not saved in the manner that most people imagine. We are saved by works - the works of Christ.
Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them." Mathew 5:17
The only way that God can be true to both His justice and His mercy is that, in Christ, He lived the life we should have lived and died the death we should have died. His justice was poured out on the Son in order for His mercy to be poured out upon us.
It's both/and. Not either/or. Christians need not be divided by such maxims, for they are both entirely true.
We are saved by grace.
One of God's graces is faith.
Eph 2:8 Yes, it was grace that saved you, with faith for its instrument; it did not come from yourselves, it was Gods gift, 9 not from any action of yours, or there would be room for pride. 10 No, we are his design; God has created us in Christ Jesus, pledged to such good actions as he has prepared beforehand, to be the employment of our lives.
For faith to be a living and abiding thing, one must follow the commandments of Christ, and perform the corporal works of mercy to enter into heaven.
James 14 Of what use is it, my brethren, if a man claims to have faith, and has no deeds to shew for it? Can faith save him then? 15 Here is a brother, here is a sister, going naked, left without the means to secure their daily food; 16 if one of you says to them, Go in peace, warm yourselves and take your fill, without providing for their bodily needs, of what use is it? 17 Thus faith, if it has no deeds to shew for itself, has lost its own principle of life. 18 We shall be inclined to say to him, Thou hast faith, but I have deeds to shew. Shew me this faith of thine without any deeds to prove it, and I am prepared, by my deeds, to prove my own faith. 19 Thou believest that there is only one God; that is well enough, but then, so do the devils, and the devils shrink from him in terror. 20 Rash soul, wouldst thou be assured that faith without deeds to shew has no life in it? 21 Think of our father Abraham; was it not by his deeds that he found approval, when he offered his son Isaac on the altar? 22 See how his faith conspired with deeds done, and through those deeds his faith was realized. 23 Thus he confirmed the words of scripture, which tell us, Abraham put his faith in God, and it was reckoned virtue in him, and he earned the title of Gods friend. 24 You see, then, that it takes deeds as well as faith if a man is to be justified.
Matthew 25:31 When the Son of Man comes in his glory, and all the angels with him, he will sit down upon the throne of his glory, 32 and all nations will be gathered in his presence, where he will divide men one from the other, as the shepherd divides the sheep from the goats; 33 he will set the sheep on his right, and the goats on his left. 34 Then the King will say to those who are on his right hand, Come, you that have received a blessing from my Father, take possession of the kingdom which has been prepared for you since the foundation of the world. 35 For I was hungry, and you gave me food, thirsty, and you gave me drink; I was a stranger, and you brought me home, 36 naked, and you clothed me, sick, and you cared for me, a prisoner, and you came to me. 37 Whereupon the just will answer, Lord, when was it that we saw thee hungry, and fed thee, or thirsty, and gave thee drink? 38 When was it that we saw thee a stranger, and brought thee home, or naked, and clothed thee? 39 When was it that we saw thee sick or in prison and came to thee? 40 And the King will answer them, Believe me, when you did it to one of the least of my brethren here, you did it to me. 41 Then he will say to those who are on his left hand, in their turn, Go far from me, you that are accursed, into that eternal fire which has been prepared for the devil and his angels. 42 For I was hungry, and you never gave me food, I was thirsty, and you never gave me drink; 43 I was a stranger, and you did not bring me home, I was naked, and you did not clothe me, I was sick and in prison, and you did not care for me. 44 Whereupon they, in their turn, will answer, Lord, when was it that we saw thee hungry, or thirsty, or a stranger, or naked, or sick, or in prison, and did not minister to thee? 45 And he will answer them, Believe me, when you refused it to one of the least of my brethren here, you refused it to me. 46 And these shall pass on to eternal punishment, and the just to eternal life.