A profound expression of gratitude emerges when a person calls upon every facet of their being, both material and spiritual, to praise God. The exact background of this song of thanks is understood in a few different ways. Some view it as King David's personal expression of gratitude for the good God bestowed upon him [מאירי]. Others suggest David is speaking on behalf of the pious among the Israelites in exile, thanking God for keeping them alive among their enemies while they hope for redemption [רד״ק, מאירי]. Another perspective highlights David's unique appreciation for his very existence. Without God's kindness, he would not have survived birth. Furthermore, David thanks God for the privilege of repairing the soul of the First Man, and for the fact that his lineage remained pure and flawless, unlike the early fathers of the nation who produced descendants like Esau and Ishmael [אלשיך].
The specific call for the soul to bless God captures the entire journey of human life. This call occurs five times throughout the psalm, corresponding to five stages a person experiences during their years. These stages range from existing as a fetus in the mother's womb, to entering the world and observing creation, all the way to the day of death. At every single phase, a person is called upon to sing and express gratitude to their Creator [רש״י, תורה תמימה].
The praise directed at God is divided into two distinct layers: the spiritual and the physical. The soul represents the higher, spiritual essence, which is a piece of the Divine from above. It thanks God for granting it the ability and understanding to grasp His glory, fulfill His Torah, and remain attached to faith [אבן עזרא, מלבי״ם, מאירי]. In contrast, the internal organs, such as the heart and kidneys, represent the physical body as a whole. The body acts as a vessel and a garment for the soul, thanking God for the peace and physical existence that allow it to support the soul in its upward journey [מאירי, מלבי״ם, רד״ק, מצודת ציון, שטיינזלץ]. Even though the physical body is formed before the soul chronologically, the soul's praise is placed first to emphasize its supreme spiritual importance as the primary essence of a human being [מאירי, אבן עזרא].
There is a subtle distinction in how these two parts of the human being offer their praise, even though the initial call to bless applies equally to both [אבן עזרא]. Because the soul is an elevated spiritual entity, it is capable of grasping the Creator Himself, and therefore it blesses God directly. The physical body, however, cannot comprehend God in a direct manner. It can only recognize Him from a distance, through His reputation and fame in the world. For this reason, the physical organs bless only His holy name, reflecting their more distant, indirect connection to the Divine [אבן עזרא, מלבי״ם].