The heart is more hilly than all else;
as is a person.
Who can understand him?
Traditional translations of Jeremiah 17.9 read differently than my translation given above. Most of them reflect an interpreted rooted in the sinful nature of the human person. For instance, the NRSV reads: “The heart is devious above all else; it is perverse– who can understand it?” The NIV reads somewhat similarly: “The heart is deceitful above all things and beyond cure. Who can understand it?” However, there are a few problems with these translations.
First, the Hebrew uses the masculine pronoun ה֑וּא in the second line, whereas the only noun reflected in most translations is לֵּ֛ב, which is a feminine noun for the heart. Consequently, it seems unlikely that the second line is referring to the heart. This leads to another problem. Most of them read as if the adjective in the second line is אָנוּשׁ, which means either incurable or disastrous according to HALOT. The issue is that in the Masoretic texts, the usual form of this does not occur. Rather, it reads with וְאָנֻ֣שׁ, lacking the shureq vowel and replacing it instead with qibbuts. While these sounds are functionally the same, the difference of form suggests that there may have been a different word here originally that the Masoretes didn’t readily identify and instead gave it the equivalent vocalic sound. Every other usage of אָנוּשׁ in Jeremiah has the shureq vowel. Likely what happened is the waw was not copied at some point in Jeremiah 17.9 and so the Masoretes had the make sense of a set of consonants that did not correspond to any known word, so they supplied the vowels associated as we have them. Yet, this leaves open the possibility that the original word could have been a different word with the same consonants. Another likely candidate is אֱנוֹשׁ, the word for a human being. The Greek Septuagint reflects this, with the second line reading as καὶ ἄνθρωπός ἐστιν (and a human is also). If the original reading was אֱנוֹשׁ, then this would explain the masculine pronoun ה֑וּא being used with that masculine noun to function as a copula. So, taking the second line to be a description of a human person eliminates some of the problems that the Masoretic Hebrew presents to us.
Secondly, the connection between the first and third line in the traditional translations is not exactly clear. If the correct rendering of עָקֹ֥ב is deceitful or perverse, then what does that immediately have to do with the inability to understand the heart? However, if the other usage of עָקֹ֥ב according to HALOT to refer to uneven of bumpy terrain is what is intended, then the connection can be more readily imagined: a highly hilly, mountainous terrain is something that conceals much behind the rises in the terrain. As a metaphor, it is understandable about such a terrain may be seen as describing someone or something that can not be readily understood. The Septuagint takes a similar line of translating עָקֹ֥ב as referring not to moral corruption but rather using it as a spatial metaphor with the word βαθεῖα that is translated as “depths.” When combined with the language of searching in v. 10
Thirdly, the traditional translations don’t really make sense of the context of Jeremiah 17. Jeremiah contrast the ultimate desolation of those who trust in human power with the well-being of those who trust in the Lord. There is no sense of moral perversity at view in this discourse, but rather there is a differentiation between the heart of different people in terms of who they trust. Then in v. 10, God is spoken of as testing the mind and searching (בחן) the heart and giving to people according to their ways. Job 28.3 describes miners as those who search out far and wide for ores. A similar connection between בֹּחֵ֣ן and עָקֹב seems much more likely, with עָקֹב being used spatially. The implication of Jeremiah’s discourse is that God is able to see who trust in human power versus those who trust in God. Other person can not possibly comprehend the nature of a person’s heart, but God has understanding of the mind and heart. As testing in the Old Testament was more about forming a person than simply revealing a person’s character, v. 10 shows how it is that God’s testing of the mind and searching of the heart leads to the well-being of those who trust in the Lord and the desolation of those who trust in human power. With that in mind, the better translation of Jeremiah 17.9 would focus on the unknowable nature of the heart of a person, except to the Lord.
The implication of this is that Jeremiah 17.9 is not really a proof-text for the universal wickedness of the human heart. The emphasis is rather on the power of God to know and test the human heart. God sees and knows what no one else can know. While we as humans can get brief glimpses of people from their words and actions, we can not really survey the whole terrain and know who people are truly and deeply. Close friends and intimate spouses regularly discover things they never understood about the object of their affection for years. However, it is only God who so deeply understands and comprehends the human heart that He can successfully test it and search out who a person trusts. Much as God tested Abraham with offering up his son Isaac to find that Abraham would come to fear God above all else, so too does God test the hearts of those who trust Him.