II. 1 Sam 15:29 And also the Strength of Israel will not lie nor relent. For He is not a man, that He should relent.”
For example 1st Samuel 15 has three uses of the word Nacham, which means repent. This word is used in the Niphal three times in the chapter. Instead of translating the word consistently, the New King James translators thought to hide the true meaning of the chapter in translating the same word regret and relent when the translation met their theological bias.
11 “I greatly regret ( נִחַ֗מְתִּי)(repent) that I have set up Saul as king, for he has turned back from following Me, and has not performed My commandments.”
29 And also the Strength of Israel will not lie nor relent (repent)( יִנָּחֵ֑ם). For He is not a man, that He should relent.”
35 the Lord regretted (נִחָ֔ם ) (repented) that He had made Saul king over Israel.
The same word in the same context is translated two different ways to hide the true meaning of the chapter. Actually, even the uneven translation does not betray the fact that God changes his mind. If he regrets making Saul king, does not that mean that if God could do it over, he would not have made Saul king? A better translation would have used the same word for all three verses and show the interrelationship between the sentences.
As to repentance, we must hold that it can no more exist in God than ignorance, or error, or impotence. …When it is said that God repented of having made Saul king, the term change is used figuratively. Shortly after, it is added, “The Strength of Israel will not lie nor repent; for he is not a man, that he should repent,” (1 Sam. 15:29). In these words, his immutability is plainly asserted without figure. 
John Calvin, Institutes of the Christian Religion
When God repents in verses 11 and 35, the term is used figuratively. When God is said not to repent, the term is without figure, Calvin argues. Apparently, Calvin’s figurative interpretation of “God repented” means the exact opposite: God does not repent. Perhaps one should be grateful Calvin refrained from changing the meaning of the word in his translation like the New King James translators would do.
Calvin has no reason not to treat verse 29, “The Strength of Isreal will not lie or repent,” as figurative. The only reason he considers verse 29 as without figure is Calvin’s bias for the Platonic view of God. He seems sensitive to the criticism that God changes his mind on some issues and not others: “The curiosity of foolish men…the counsel of God is not firm or stable, but varies with the changes of sublunary affairs…..” Does he defend these views with sound exegesis, in depth word studies or reasoned arguments?
Calvin defends immutability with the only weapons he has, intimidation and personal attacks (curiosity of foolish men). When one does not have an argument these are the only tools left. Of course God explains that he changes his mind, but Calvin just denies the evidence and proclaims the opposite. It is not exegesis to proclaim loudly, “repentance, we must hold that it can no more exist in God than ignorance, or error, or impotence.” If someone were bold enough to actually believe what Scripture says, then he would be guilty of blasphemy against God, accusing God of ignorance, or error, or impotence. This is simply a denial of what Scripture says.
The proper way to interpret verse 29 comes through context. God will not repent (change his mind) about taking away the Kingship from Saul. He will change his mind about giving the kingship to Saul. This interpretation does not have to treat any part of the chapter as figurative or metaphoric. Note, however, this is not a metaphor or figurative in any normal sense of the words. This is a plain statement. “God repented” is without any metaphor.