Everyone Ever

Sometimes people say things like "In the old testament they were saved by the Law,  and in the new testament by Grace ", But scripture over and over again refutes this mindset.  Look at this passage in Acts 2 that refers to David. 

Acts 2
“For David says of Him, ‘I SAW THE LORD ALWAYS IN MY PRESENCE; FOR HE IS AT MY RIGHT HAND, SO THAT I WILL NOT BE SHAKEN. 26‘THEREFORE MY HEART WAS GLAD AND MY TONGUE EXULTED; MOREOVER MY FLESH ALSO WILL LIVE IN HOPE; 27BECAUSE YOU WILL NOT ABANDON MY SOUL TO HADES, NOR ALLOW YOUR HOLY ONE TO UNDERGO DECAY. 28‘YOU HAVE MADE KNOWN TO ME THE WAYS OF LIFE; YOU WILL MAKE ME FULL OF GLADNESS WITH YOUR PRESENCE.’  29¶“Brethren, I may confidently say to you regarding the patriarch David that he both died and was buried, and his tomb is with us to this day. 30“And so, because he was a prophet and knew that GOD HAD SWORN TO HIM WITH AN OATH TO SEAT one OF HIS DESCENDANTS ON HIS THRONE, 31he looked ahead and spoke of the resurrection of the Christ, that HE WAS NEITHER ABANDONED TO HADES, NOR DID His flesh SUFFER DECAY.

David kept faith in the coming Christ and regarded the resurrection. David was saved the same way as everyone else in the New Testament,the same way you or I am saved. By grace through faith. The love for the commands of God were and are a love for God in response to salvation,  not the means of its acquisition.

Psalms 119
My eyes fail with longing for Your salvation And for Your righteous word. 124 Deal with Your servant according to Your lovingkindness And teach me Your statutes. 125 I am Your servant; give me understanding, That I may know Your testimonies.

David looks to Christ for Salvation by faith, by God's lovingkindness, or as it were- Grace. David wasn't the only one either. 

Acts 3
Moses said, ‘THE LORD GOD WILL RAISE UP FOR YOU A PROPHET LIKE ME FROM YOUR BRETHREN; TO HIM YOU SHALL GIVE HEED to everything He says to you. 23‘And it will be that every soul that does not heed that prophet shall be utterly destroyed from among the people.’ 24“And likewise, all the prophets who have spoken, from Samuel and his successors onward, also announced these days. 25“It is you who are the sons of the prophets and of the covenant which God made with your fathers, saying to Abraham, ‘AND IN YOUR SEED ALL THE FAMILIES OF THE EARTH SHALL BE BLESSED.’

Galatians 3
8The Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, “ALL THE NATIONS WILL BE BLESSED IN YOU.” 9So then those who are of faith are blessed with Abraham, the believer.

Abraham and the prophets were saved by faith through grace with the same gospel. Peter testifies that all the Prophets knew Christ for salvation 

Acts 10:43
“Of Him all the prophets bear witness that through His name everyone who believes in Him receives forgiveness of sins

Hebrews 11 states it outright that these Patriarchs walked by faith in God. 

 Hebrews 11
4 By faith Abel offered to God a better sacrifice than Cain, through which he obtained the testimony that he was righteous, God testifying about his gifts, and through faith, though he is dead, he still speaks. 5 By faith Enoch was taken up so that he would not see death; and he was not found because God took him up; for he obtained the witness that before his being taken up he was pleasing to God. 6 And without faith it is impossible to please Him, for he who comes to God must believe that He is and that He is a rewarder of those who seek Him. 7 By faith Noah, being warned by God about things not yet seen, in reverence prepared an ark for the salvation of his household, by which he condemned the world, and became an heir of the righteousness which is according to faith. 8 By faith Abraham, when he was called, obeyed by going out to a place which he was to receive for an inheritance; and he went out, not knowing where he was going. 9 By faith he lived as an alien in the land of promise, as in a foreign land, dwelling in tents with Isaac and Jacob, fellow heirs of the same promise; 10 for he was looking for the city which has foundations, whose architect and builder is God. 11 By faith even Sarah herself received ability to conceive, even beyond the proper time of life, since she considered Him faithful who had promised. 12 Therefore there was born even of one man, and him as good as dead at that, as many descendants as the stars of heaven in number, and innumerable as the sand which is by the seashore.
... 17 By faith Abraham, when he was tested, offered up Isaac, and he who had received the promises was offering up his only begotten son; 18 it was he to whom it was said, “In Isaac your descendants shall be called.” 19 He considered that God is able to raise people even from the dead, from which he also received him back as a type. 20 By faith Isaac blessed Jacob and Esau, even regarding things to come. 21 By faith Jacob, as he was dying, blessed each of the sons of Joseph, and worshiped, leaning on the top of his staff. 22 By faith Joseph, when he was dying, made mention of the exodus of the sons of Israel, and gave orders concerning his bones. 23 By faith Moses, when he was born, was hidden for three months by his parents, because they saw he was a beautiful child; and they were not afraid of the king’s edict. 24 By faith Moses, when he had grown up, refused to be called the son of Pharaoh’s daughter, 25 choosing rather to endure ill-treatment with the people of God than to enjoy the passing pleasures of sin, 26 considering the reproach of Christ greater riches than the treasures of Egypt; for he was looking to the reward.

Note clearly that it says that Moses considered the reproach of Christ. 
This is directly opposed to the idea that people were saved by works in the Old Testament or that adherence to the Law of God was for salvation. 

Everyone ever has been saved by Grace through Faith and its never been the case that it was by adherence to the Law of God.