Our Gemara on Amud Aleph discusses the extraordinary integrity of Rabbi Safrah. His standard of honesty was so high, that even if he only resolved in his mind to make a sale at a certain price, he would stick with his inner resolution, despite the buyer revealing that he would be willing to pay more. This kind of practice is considered one of many ways that a person “speaks the truth in his heart.”

 

The idea of “speaking the truth in one's heart” is based on a verse in Tehilim (15:2). The commentaries offer a number of other intriguing ways to fulfill the idea of speaking truth in one’s heart.

 

For example, Radak, on this verse warns against accepting things only on faith, as that cannot be a full truth in one’s heart. If one is not deeply convinced of something and does not allow for intellectual exploration and logical consideration, their belief can be shallow. He holds it is a responsibility of a religious person to not just believe, but to come up with reasons and rationale that support the belief and make it stronger. 

 

There is an old argument amongst Jewish thinkers with some holding that simple faith is superior, while others, following the path of the Radak and other Spanish Rishonim maintain the importance of having knowledge that comes from intellectual conviction. The introduction to the Lev Tov edition of the Chovos Halevavos where you can find an anthology of different opinions and source materials throughout the ages.

 

Likkutei Halachos, CM, Laws of Theft (5:21, 51) understands the idea of “speaking truth in one heart” in a new and creative way. He says one of the reasons that tattoos are forbidden is because the idolaters would demonstrate their faith with ostentatious acts, such as tattooing demonstrations of faith on their body. This does seem to be an archetypal pattern of human behavior, witness the phenomenon of pop stars, enamored of Kabbalah, tattooing the Tetragrammaton on their bodies. 

 

Additionally, nighttime is a period of fear and confusion. It represents when God is hidden. At night a person cannot navigate by what he readily sees and is apparent, so he must rely on intuition and inner wisdom. Symbolically, this is why morning and afternoon prayers were legislated as obligations, while the evening prayer was originally instituted as voluntary (see Berachos 27b, although the custom now is to treat it  an obligation, see Mishna Berurah 106:4.) The idea of being, that the truth in the heart can only be arrived at intuitively by each person in their own way, and cannot be mandated in a uniform manner. This is why seeking God at night was not made into an obligatory prayer.

 

The idea that real truth is found by looking inward, and sensing in the heart, is reminiscent to Me of the quiet, still voice that God uses to manifest himself in Melachim (I:19:11-12):

 

“Come out,” He called, “and stand on the mountain before GOD.”And lo, GOD passed by. There was a great and mighty wind, splitting mountains and shattering rocks by GOD’s power; but GOD was not in the wind. After the wind—an earthquake; but GOD was not in the earthquake. 

 

After the earthquake—fire; but GOD was not in the fire. And after the fire—a soft quiet sound. 

 

Ironically, as we often find in Jewish philosophy, the very same texts are used to prove one point and its opposite by a different group. For example, here Likkutei Halachos uses the phrase “truth in the heart” to connote an intuitive truth found inside, not a logical and reasoning truth.