Dramatic divine intervention abruptly halts the natural course of events in the Egyptian palace. God's providence acts immediately to preserve Sarah's purity and punish her captors. The primary approach among commentators is that Pharaoh suffered an actual, severe physical disease. This specific illness made physical intimacy impossible, effectively preventing him from harming Sarah [רש״י, מזרחי, גור אריה]. A contrasting view suggests that these were not physical blows, but rather a severe warning and threat, given that Pharaoh had not yet actually committed a sin [רבנו בחיי בשם רס״ג].
The suddenness of this punishment stands in stark contrast to the later story of Abimelech, who received a divine warning in a dream. Pharaoh was struck immediately because he acted out of sheer lust, taking Sarah by force, leaving an immediate physical affliction as the only way to stop him [פענח רזא]. Furthermore, while Abimelech was a decent ruler who investigated matters, Pharaoh was deemed unworthy of a divine revelation. He was punished for failing to properly investigate the marital status of the woman he brought into his home [דברי דוד, קאסוטו, ברטנורא].
The punishment extended beyond the king to his entire household and his ministers. They suffered because they were active participants who had praised Sarah and assisted in taking her to the palace [רד״ק, שפתי כהן, קאסוטו]. However, Pharaoh suffered severe afflictions, while his household experienced lighter ones. This clear distinction demonstrated to everyone that this was not a random, natural plague, but a deliberate punishment from God, especially as they watched the righteous woman herself remain completely unharmed [ספורנו, מלבי״ם, גור אריה]. One perspective even suggests the devastation was so comprehensive that it struck the very walls, pillars, and vessels of the palace [רש״י].
The plagues were brought about directly on Sarah's account, which some interpret as being triggered by her actual words. According to one approach, the blows were delivered by her command; she would instruct an angel to strike, and the angel would carry out the punishment on Pharaoh [רש״י, מזרחי]. Another interpretation suggests this refers to Sarah's desperate pleas to Pharaoh himself. Realizing the danger, she cried out and confessed that she was a married woman. Pharaoh refused to believe her, choosing instead to rely on the initial claim that she was merely a sister, and was struck immediately for ignoring her cries [כלי יקר, אלשיך].
The sudden onset of these specific plagues, particularly an illness preventing physical intimacy, forced Pharaoh to recognize the hand of God. He examined his own actions, suspected that his captive might be a married woman, and demanded the truth from Sarah, finally discovering that she was indeed Abraham's wife [רמב״ן, רד״ק, קאסוטו]. Alternatively, some suggest that at the exact moment the plagues struck, God Himself directly revealed to Pharaoh that she was a married woman [אור החיים, טור הארוך].