God's true expectation of His people centers not on bringing sacrifices or singing hymns, but on building a proper society based on honesty and morality [אבן עזרא, רד״ק, מלבי״ם]. As an alternative to the rejected sacrificial offerings, the demand is for the values of justice and kindness to well up and wash over the land.
When it comes to how this justice should appear, there are two primary ways to understand the prophet's call. One perspective views it as an act of uncovering. Justice, which the people had suppressed, corrupted, or kept hidden in the shadows, must be brought into the light for all to see. It must spread and wash over the earth, much like water bursting forth from deep underground [רש״י, מצודת דוד, מצודת ציון, שטיינזלץ, אברבנאל]. Another perspective understands this call as an act of continuous movement. In this view, justice is meant to surge and roll forward rapidly, flowing like spring water without facing any barriers or delays [אבן עזרא, רד״ק].
Alongside this call for justice is the demand for righteousness, which must flow like a strong, unyielding river. Because the people had stopped performing acts of goodness, these actions must be restarted and maintained with great strength. They are compared to a rushing river whose waters are permanent and constant, never drying up or failing [מצודת דוד, מצודת ציון, רד״ק, שטיינזלץ, אברבנאל].
A deep philosophical difference exists between justice and righteousness, reflected in the different ways they are compared to water [מלבי״ם]. Justice deals with the relationships between people. It is rooted in human logic and our natural social needs, as no healthy society can exist without it. Therefore, it is compared to water that bubbles up naturally from an internal spring and flows outward toward others. Righteousness, on the other hand, represents the relationship between a person and God. It does not come from basic human nature but from a divine command meant to bring spiritual perfection to the person performing it. For this reason, it is compared to a riverbed that has no water source of its own but must be filled by water gathering from the outside, such as from mountaintops. There is a natural order to this process: logical justice must come first. Only when a person allows justice to flow naturally from within does it awaken the divine blessing that fills the riverbed with righteousness.