From Sahih Muslim (Hadith 2131):
This hadith has been narrated by Khalid al Hadhdha' with the same chain of transmitters but with this alteration that he said:(O Allah! ) let Thee be the caretaker of what is left by him, and he said: Grant him expansion of the grave, but he did not say: Make his grave spacious. Khalid said: He supplicated for the seventh (thing too) which I have forgotten
Reference: Muslim 2131