From Sahih Muslim (Hadith 3250):
A'isha reported:I asked Allah's Messenger (ﷺ) about Hijr, and the rest of the hadith is the same. I also said: Why is it that the door has been made on a higher level, and one cannot (get into it) but with the help of a ladder? The rest of the hadith is the same as reported above and the concluding words are: (I do not change it) out of the apprehension that their hearts may disapprove of it
Reference: Muslim 3250