Both the New and Old Testaments are covenants, which require at least two parties.
Eph 2:8-9 For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast.
It is by the grace of God that we are saved. This grace is the unconditional forgiveness of sins freely given to all mankind by God.
But in order that our sins are forgiven (salvation), we must have faith in God. So
Salvation = Grace + Faith
Note - Faith is the response of their belief in the Grace given by God.
Though grace is given freely to all men, yet only Christians who responded by having, expressing or displaying their faith in God's grace receive salvation.
Not of Works
Many try to appease God by sacrifices, offerings and doing charities, etc. hoping that these good works can save them. To the Almighty God, these are dead works (Heb 6:1, 9:14) for He has already given to everyone the equal chance of salvation through His grace.
What is faith towards God?
Heb 11:1 Now faith is the substance of things hoped for, the evidence of things not seen.
Faith is the substance (action) expressing the hope or belief in God. We have to walk (perform, work, do, action, response, etc,) by faith towards God in accordance to His words, commands, covenant, will, promise, etc.
2Cor 5:7 For we walk by faith, not by sight.
Heb 11:7 By faith Noah, being divinely warned of things not yet seen, moved with godly fear, prepared an ark for the saving of his household, by which he condemned the world and became heir of the righteousness which is according to faith.
The building of the ark (response or work) to save his family was the faith of Noah towards God.
Heb 11:8 By faith Abraham obeyed when he was called to go out to the place which he would receive as an inheritance. And he went out, not knowing where he was going.
Abraham leaving Ur (response or work) was his faith towards God.
Heb 11:17 By faith Abraham, when he was tested, offered up Isaac, and he who had received the promises offered up his only begotten son,
Offering of Isaac as sacrifice (response or work) was Abraham's faith towards God.
Jam 2:21 Was not Abraham our father justified by works when he offered Isaac his son on the altar?
Heb 11:31 By faith the harlot Rahab did not perish with those who did not believe, when she had received the spies with peace.
Rahab receiving the spy with peace (response or work) was her faith towards the God of Abraham.
Jam 2:25 Likewise, was not Rahab the harlot also justified by works when she received the messengers and sent them out another way?
Jam 2:19 You believe that there is one God. You do well. Even the demons believe—and tremble!
The demons too believe that there is one God, but did not respond nor confess nor accept it (no work), because Satan himself wants to be God.
Jam 2:26 For as the body without the spirit is dead, so faith without works is dead also.
Faith = Belief + Work(response)
We are saved by faith, i.e believe in Jesus as the propitiation of our sins and accept (response or work) Him as our Lord and Saviour.
Brethren, no matter how much we can sacrifice to please God - with all types of good offerings and righteous works, there is no salvation besides the grace through faith in our Lord Jesus Christ, the sacrificial Lamb of God.