The arrival of the great day of judgment is a terrifying event that puts humanity to an ultimate existential test. It is a time of deep and absolute purification, where good and evil are separated through fierce, uncompromising means. The immense difficulty of surviving the revelation of the clearing angel is emphasized by asking who can endure or bear the weight of this event, and who has the strength to hold on and remain alive [רש״י, מצודת ציון, שטיינזלץ].
The primary approach among commentators is that this repetition of survival simply strengthens the warning. However, others see a clear progression. According to [מלבי״ם], the event unfolds in two distinct stages. The first stage is the overwhelming fear felt from the mere approach of the day, even before anything is revealed. The second stage is the actual moment of revelation, an experience so intense that no living creature can withstand it. Taking a different approach, [אברבנאל] views the first stage as a description of the general destruction that will occur on God's day, while the second stage specifically addresses how the Israelites will stand in judgment during that time.
To illustrate how this day of judgment operates, two distinct images of cleaning and purification are presented. The first is a refiner's fire, the intense heat used to purify metals. Just as fire burns away the waste and leaves behind only pure silver, the day of judgment will separate the righteous from the wicked, completely destroying the rebels and sinners [מצודת דוד, רד״ק]. This mirrors the prophecy of Zechariah, which speaks of passing the nation through fire in order to sort them [אבן עזרא, רד״ק, אברבנאל].
The second image is launderers' soap, a harsh herb or cleaning agent used by washers to scrub away stubborn stains, inherently linked to the concept of total cleanliness and purity [רש״י, מצודת ציון, שטיינזלץ]. The primary approach among commentators is that both the fire and the soap represent the exact same action: the complete eradication of the wicked, who are viewed as a stain that must be removed from the world [רש״י, רד״ק].
However, [מלבי״ם] offers a striking distinction between the two materials. He explains that the refiner's fire is meant to entirely consume the wicked, who are considered absolute waste. In contrast, the soap is intended for the righteous. Just as soap removes a minor stain from a garment to leave it perfectly clean and white, the day of judgment will gently wash away any slight flaw that may have attached itself to the righteous.