וַיִּשְׁלַ֥ח שָׁא֛וּל מַלְאָכִ֖ים לָקַ֣חַת אֶת־דָּוִ֑ד וַתֹּ֖אמֶר חֹלֶ֥ה הֽוּא׃ (פ)
And when Saul sent messengers to take David, she said: ‘He is sick.’
Rashi
and they guarded the house when Michal told them that he was ill (I Sam. 19:14) and she allowed him to flee at night.