Deep within the belly of the fish, surrounded by darkness and distress, a profound shift occurs. Rather than despairing, a deep sense of absolute loyalty to God emerges, accompanied by a firm commitment to give thanks for the miracle of survival and an acceptance of the divine mission.
Even in the midst of severe trouble, a steadfast faithfulness remains [ביאור שטיינזלץ]. While still trapped inside the creature, hoping to eventually emerge alive, a solemn promise is made to God [אבן עזרא, ביאור שטיינזלץ]. The commitment is to bring thanksgiving sacrifices and to publicly acknowledge the great miracle in the presence of the congregation [מצודת דוד, רד״ק]. This pledge to offer thanks is especially fitting, as those who travel the sea are traditionally among those obligated to express public gratitude to God [מלבי״ם].
Regarding the exact nature of this promise, the primary approach among commentators is that it refers to a strict commitment to bring the physical thanksgiving and peace offerings that were pledged [רש״י, רד״ק]. However, an alternative perspective broadens the meaning of this vow. Instead of focusing solely on sacrifices, the vow is seen as a renewed commitment to fulfill the very command that was originally abandoned: the mission to go to Nineveh [מלבי״ם].
The conclusion of this prayer is a powerful declaration that salvation rests entirely in divine hands. The promised sacrifices are specifically dedicated to the act of rescue that God performed [רש״י, מצודת דוד]. It is a clear and absolute recognition that deliverance belongs to God alone, as He is the sole author of this immense, miraculous rescue [רד״ק, ביאור שטיינזלץ].
Beyond the immediate personal rescue, this final declaration resolves the underlying tension that caused the initial flight. Originally, the refusal to travel to Nineveh stemmed from a deep fear that saving the city would eventually bring harm to the Israelites at the hands of the Assyrian king. Now, having experienced firsthand that salvation belongs entirely to God, there is a newfound trust and hope that God will ultimately save the Israelites from all their future troubles as well [מלבי״ם].