English: Sacred Heart of Jesus. The legend cites Psalm 63:7, Accedet homo ad cor altum (modern numbering: Psalm 64:6)

This is a difficult verse, and the Latin translation is based on LXX, προσελεύσεται ἄνθρωπος καὶ καρδία βαθεῖα, the altum here expressing "deep, profound", not "high, elevated". The original has: וְקֶרֶב אִישׁ וְלֵב עָמֹֽק

The KJV, based on the Hebrew directly, attempts "both the inward of every one , and the heart, deep", and the modern understanding of the Hebrew text now has the "deep heart" (לֵב עָמֹֽק) refer to human hubris, not to a pious or mystical "ascent of the heart", Knox translation: "Let the thoughts of man’s heart be deep as they will / yet God has arrows, too, to smite them with, sudden wounds to deal them", Haydock Commentary "Heart. That is, crafty, subtle, deep projects and designs; which nevertheless shall not succeed; for God shall be exalted in bringing them to nought, by his wisdom and power."

But in early modern interpretation, the Latin text was interpreted in mystical terms of the Sacred Heart (apparently based on a "pun" by Saint Bernhard), or as Christ, as Man, "ascending" to the "Secret Heart", which is apparently the subject matter expressed in this allegorical painting.