It is narrated that a person asked Imam Ali (AS):

Is your God able to place the world in an egg without the world becoming small or the egg becoming big? Imam Ali (AS) replied: Allah (SWT) is never described as weak and unable, but what you have asked is impossible [1]. In another narration, the same question was asked from Imam Ridha/Reza (AS), and Imam (AS) replied: Yes, Allah (SWT) can and is able to do it in smaller than that (an egg). Can you not see that God has placed the world in your eyes whilst it is smaller than an egg [2]?

[1] Beharul Anwaar, Vol. 4, Page 143.

[2] Payam-e-Quran, Ayatollah Makarem Shirazi, Vol. 4, Page 178.

Source: en.shafaqna.com