וַיֹּאמַ֗ר הָגָ֞ר שִׁפְחַ֥ת שָׂרַ֛י אֵֽי־מִזֶּ֥ה בָ֖את וְאָ֣נָה תֵלֵ֑כִי וַתֹּ֕אמֶר מִפְּנֵי֙ שָׂרַ֣י גְּבִרְתִּ֔י אָנֹכִ֖י בֹּרַֽחַת׃
И сказал он: 'Агарь, Сара'служанка, откуда ты пришел? и куда ты идешь?' И она сказала: 'Я убегаю от лица моей любовницы Сары.'
Rashi
אי מזה באת WHENCE CAMEST THOU? — He knew it, but he asked this in order to give her a starting-point so that he might converse with her. The expression אי מזה is to be explained thus: Where is (אי) that place of which thou canst say, “From this (מזה) have I come”.
Chizkuni
הגר שפחת שרי, “Hagar, Sarai’s servant maid!” The angel reminds her that her status as Sarai’s servant maid had not changed. She acknowledged this when she replied that she was fleeing from her mistress Sarai.
Sforno
?אי מזה באת ואנה תלכי, the angel wanted Hagar to realise what kind of an unprofitable exchange she was about to make if she left the house of a man such as Avram and traded that holy environment in the land of Canaan, preferring the spiritually contaminated regions outside the Holy Land and the evil people residing there.