It is recommended for a Muslim to perform Hajj as soon as he can afford it. But, it is also acceptable to perform `Umrah without or before performing Hajj. However, one should know that performing `Umrah does not exempt him from offering Hajj as `Umrah is only sunnah while Hajj is fard.
A well detailed response was given on this issue by Sheikh Sayyed Sabiq in his Fiqh As-Sunnah, as thus:
“A person may perform `Umrah during the months of Hajj, without performing Hajj. `Umar Ibn Al-Khattab performed `Umrah during the month of Shawwal and returned to Madinah without performing Hajj. By analogy, one may, like `Umar, perform `Umrah even before the time of Hajj.
Tawus said, “In the Pre-Islamic Era, the Arabs considered performing `Umrah during the months of Hajj as one of the major sins. And they used to say, ‘When (the month of) Safar ends, and the camels are back, and wounds in their legs are healed, and when traces of footprints (of pilgrims) are effaced, then one wishing to perform `Umrah may do so.’”
After the advent of Islam, people were commanded to perform `Umrah even during the months of Hajj. Thus, `Umrah was permitted during the months of Hajj until the Day of Judgment.
Time for `Umrah:
The majority of scholars are of the opinion that `Umrah may be performed at any time during the year. Abu Hanifah, however, is of the view that it is disliked to perform `Umrah on five days, namely the Day of `Arafah, the Day of Nahr (the 10th of Dhul-Hijjah), and the three days of Tashriq (11th, 12th, and 13th of Dhul-Hijjah).
Abu Yusuf considers it disliked on the Day of `Arafah and the three following days. All of them, however, agree on the permissibility of performing `Umrah during the months of Hajj.
Al-Bukhari has reported on the authority of `Ikrimah Ibn Khalid who said, “I asked `Abdullah Ibn `Umar about performing `Umrah before Hajj, whereupon he said, ‘There is no harm in doing so, because the Prophet (peace and blessing be upon him) himself performed `Umrah before Hajj.’”
Jabir reported that `A’ishah’s menstruation started while she was performing Hajj, but she performed all the rites of Hajj except Tawaf around the Ka`bah. When her period ended and she was clean, she performed the Tawaf, and said, “O Prophet of Allah! Everyone has performed Hajj and `Umrah together, but I have performed Hajj only.” Thereupon the Prophet (peace and blessings be upon him) instructed her brother `Abdur-Rahman to accompany her to Tan`im (in order to perform `Umrah). So she performed `Umrah right after Hajj in the month of Dhul-Hijjah.
It goes without saying that the best time to perform `Umrah is during the month of Ramadan.”