"Let us be sure of this: we will not long preserve the gospel without the languages. The languages are the sheath in which this sword of the Spirit is contained... If through our neglect we let the languages go (which God forbid!), we shall... lose the gospel" –Martin Luther
I was talking with a friend the other day about how sometimes I get discouraged thinking about how much time I've spent learning the languages, because of how hard it is to make things relevant for the typical brother or sister. [I'm not talking about these pseudo-word studies pastors perform when on stage... I'm talking about real exegesis]. You have to really know your stuff to be able to contribute in a real way for some buddies in a bible study—and, please don't hear this with anything but candidness, most who have dipped their foot in the waters of the languages (through a couple courses in seminary), don't know their stuff... even though they might think they do. I know enough to know I need to be cautious, and I just might know enough to know when I don't know something (but that's still up for debate).
So as I was confessing this to him, he brought up a sermon he'd heard recently preached from Gen 22.16 where the angel of God reiterates his promises to Abraham of expanding His kingdom through this man from Ur—in light of what recently took place with willingness to snuff out his own seed through Isaac.
According to our inherited story, you get the impression that this willingness to put his own son in the grave made God jittery with excitement:
"I do declare! [Think, Scarlett O'Hara in "Gone with the Wind"; or better, Steve Carrel in "The Office"], since you've done this thing of not withholding your son, your only one!—I am seriously gonna bless you, and multiply and multiply your children!
Now in this sermon my friend was telling me about, the preacher argued that a little word in the Hebrew Bible—כי (kî)—should not be translated as "because" or "since" but as "that". So in her exegesis, she argued for a translation along the lines of...
I have sworn by myself that you've done this thing of not withholding your son, your only one, that I will surely bless you and surely multiply your offspring.
In doing so, she argues that this interpretation reveals that God's faithfulness is (scripturally) protected, that the promise to Abraham isn't based on his obedience in offering up Issac (implying her presupposition that if kî is translated because that this implies God might not have followed through with his original promise; thus, jeopardizing God's faithfulness).
While this may be a convenient flow of thought (for a Western, "rational" mind), it certainly doesn't hold up to what's explicitly stated in the Hebrew text.
בִּי (by myself) נִשְׁבַּעְתִּי (I swear) נְאֻם־יְהוָה (declares Yhwh) כִּי (that) יַעַן (because) אֲשֶׁר (which) עָשִׂיתָ (you have done) אֶת־הַדָּבָר (thing) הַזֶּה (this)
I'm not sure how much Hebrew the preacher knows—for she's correct in stating that kî can be translated as "that" or "because/since"—but you cannot just pick at a whim which grammatical function you wish to see utilized in a text, for whatever theological agenda you wish to promote. No: Biblical Hebrew is a language just like any other, and like all languages, there is a rational (grammatical) flow that is to be recognized.
Sometimes it can get sticky accounting for a language's grammar—especially when the language is one no longer spoken, like Biblical Hebrew—but sometimes, we get lucky and interpreting really isn't that hard to do. Genesis 22.16 is one of these times, if we're looking at whether or not kí should be translated as "that" or "because".
[I'll keep this simple for those who may barely be following along (since they don't rummage around in Hebrew) and for those who want to explore more, do so in the comments or engage with the references I give.]
Kî is used twice in the immediate context of vs. 16: once in vs. 16 and once in vs. 17. In both times it should (in congruence with the pastor's thoughts) be translated as "that"—because it is introducing a content clause after a verb that deals with talking (i.e. "he said, I swear"); in other words, the kî points to the following information as being the content of what is said (e.g. "I told the waiter that I wanted sweet potato fries"). [For you Hebrew gurus, look up WO 38.8d]
Now this is where the preacher stopped her argument: "Kî means "that"; and God didn't reiterate his promise because of Abraham's obedience, because God is faithful no matter." However, in whatever her exegetical endeavors entailed in consulting the Hebrew bible, what she failed to see was the following word, just after kî—for this little Hebrew word completely destroys her argument. The word is יען (ya'an), and according to several go-to sources of Biblical Hebrew lexicography (e.g. BDB or HALOT) says that this lexeme, especially when followed by אשׁר (which is the case in vs. 16), always indicates that the ensuing clause is one that describes the purpose, cause or intention of a pre/pro-ceeding action.
In this case, that means that no matter how kî is understood, the fact that God is gonna seriously bless and multiply Abraham's kiddos is directly tied, in a causal way, to Abraham's giving up of his only boy. This is explicitly communicated through the Hebrew word ya'an. There's no way around this. We can wrestle out what this means theologically, but we can't—if we're being true to the Bible—simply opt out of any cause-a/effect relationship between these two statements, viz. God is gonna do X because Abraham did Y.
After I had this discussion with my friend, he felt much better about the uneasiness he felt when listening to the preacher's sermon. And I, also, felt much better having seen my knowledge of Hebrew put to good, practical use. It was a win-win for both of us. :)
I hope that you, and myself, see more and more how important the sheath is for the Sword.
In answer to the question I raised in the post's title, my answer is: Of course! God is faithful whether we are or aren't—but, he's not necessarily gonna be happy about fulfilling his word to some faithless son. He's in relationship with us, just like he was with Abraham. The text of Gen 22.16–17 is clear: God got excited over Abraham's attempt to be obedient. The fulfillment of His promise was never on the line! But the condition of the relationship between the two, the level of intimacy and trust, is always going to be a variable, contingent upon our trust in Him. Remember: without faith, it's impossible to please Him. With that said, while there may be no cause-effect relationship between Abraham's obedience [cause] and God's follow-through [effect], there is certainly a cause-affect relationship; that is, Abraham's obedience is the cause of a great heartfelt affect in God's response and reiteration of his older promises. (For you Hebrew nerds out there, the double infinitive absolutes attest to the excitement and intensity of God's reaffirmation of his promises, viz. God says, "I'm seriously gonna bless you, and I'm gonna multiply and multiply and multiply your children!).