These are the worst examples of backsliding and justification I have seen.
King David Believed in Jesus
The claim that King David believed in Jesus Christ (had faith in Jesus Christ)
Arose out of the Romans 3:9-20 vs Psalms 14/Psalms 53 controversy.
He was unwilling to admit that despite the “gear shift” it is clear that Paul misinterpreted Psalms 14 and that on both sides of Psalm 14 the message is opposite of Paul's.
The Christian then argued that King David had faith in Jesus and “believed in Jesus Christ.”
He used Romans 3:21-31 to justify this claim even though Romans 3:21-31 depended on the truth of 3:9-20; in other words he was engaging in circular reasoning;
if romans 3:9-20 is in question it cannot be used to justify a belief in 3:21-31 which is then used to back-justify 3:9-20.
He was unable to justify the 3:9-20 discrepancy in any other way. In the end he got angry because I did not accept his explanation that King David believed in Jesus.
Abraham was justified by Faith
In every case it occurs the Christian is simply operating from a position of misinformation.
1. The verse is surrounded by Abraham apparently “doubting” God:
2 But Abram said, “O Lord God, what will you give me, for I continue[a] childless, and the heir of my house is Eliezer of Damascus?” 3 And Abram said, “Behold, you have given me no offspring, and a member of my household will be my heir.”
7 And he said to him, “I am the Lord who brought you out from Ur of the Chaldeans to give you this land to possess.” 8 But he said, “O Lord God, how am I to know that I shall possess it?”
2. The verse itself in context does not mean what Chrisitians assume it to mean:
5 And he brought him outside and said, “Look toward heaven, and number the stars, if you are able to number them.” Then he said to him, “So shall your offspring be.” 6 And he believed the Lord, and he counted it to him as righteousness.
So this isn't the kind of faith that Abraham believed anything other than God would keep his promises. This is entirely different from the kind of faith Christians talk about.
3. In context, Abraham actually didn't believe God even at all
The point is that he wondered if he would have descendants even though God already promised him. Then after that he also doubted that he would even posses the land(!!)
4. It should also be very clear from a study of Abraham that he passed 10 tests by action and not by belief – therefore the Christian claim does not hold – to say Abraham was justified by faith is incredulous.