Jeremiah 17:10
8 They will be like a tree planted near a stream whose roots spread out toward the water. It has nothing to fear when the heat comes. Its leaves are always green. It has no need to be concerned in a year of drought. It does not stop bearing fruit. 9 The human mind is more deceitful than anything else. It is incurably bad. Who can understand it? 10 I, the Lord, probe into people’s kidneys10. I examine people’s hearts. I deal with each person according to how he has behaved. I give them what they deserve based on what they have done. 11 The person who gathers wealth by unjust means is like the partridge that broods over eggs but does not hatch them. Before his life is half over, he will lose his ill-gotten gains. At the end of his life, it will be clear he was a fool.” 12 Then I said, “Lord, from the very beginning you have been seated on your glorious throne on high.You are the place where we can find refuge.
Revelation 2:23
21 I have given her time to repent, but she is not willing to repent of her sexual immorality. 22 Look! I am throwing her onto a bed of violent illness, and those who commit adultery with her into terrible suffering, unless they repent of her deeds. 23 Furthermore, I will strike her followers with a deadly disease, and then all the churches will know that I am the one who searches kidneys* and hearts. I will repay each one of you what your deeds deserve. 24 But to the rest of you in Thyatira, all who do not hold to this teaching (who have not learned the so-called “deep secrets of Satan”), to you I say: I do not put any additional burden on you. 25 However, hold on to what you have until I come.
Notes and References
"... God wants the churches to know ὅτι ἐγώ εἰμι ὁ ἐραυνῶν νε ροὺς καὶ καρδίας (hoti egō eimi ho eraunōn nephrous kai kardias, that I am the one who searches the feelings and the thoughts). When Christ “searches” a person, he makes a critical investigation that lays bare the deepest part of a person’s being. The language is reminiscent of Jer. 17:10, “I the LORD search the heart and examine the mind.” The νε ρός is literally the “kidney,” in Hebrew thought the core of emotions and feelings. The καρδία is the seat of the intellect and mind. Together they constitute one’s inner being. Nothing can be hidden from the inquiry of the Lord. Therefore, “all churches” had better examine their own house, lest the same judgment befall them, for they will not get away with their sins ..."
Osborne, Grant R. Baker Exegetical Commentary: Revelation (p. 133) Baker Academic, 2019