وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ افْصِلُوا بَيْنَ حَجِّكُمْ وَعُمْرَتِكُمْ فَإِنَّ ذَلِكَ أَتَمُّ لِحَجِّ أَحَدِكُمْ وَأَتَمُّ لِعُمْرَتِهِ أَنْ يَعْتَمِرَ فِي غَيْرِ أَشْهُرِ الْحَجِّ ‏.‏

Yahya related to me from Malik, from Nafi, from Abdullah ibnUmar, that Umar ibn al-Khattab said, "Keep your hajj separate fromyour umra. That way your hajj will be more complete. And your umrawill be more complete if you do it outside of the months of the hajj." Translation Not Available

Book Ref: Muwatta Imam Malik Book 20 Hadith 772
Web Ref:  Muwatta Imam Malik Book 20 Hadith 68