Muwatta Malik, Book 20, Hadith 772 (In-Book) ⓘ

Yahya related to me from Malik, from Nafi, from Abdullah ibn Umar, that Umar ibn al-Khattab said, "Keep your hajj separate from your umra. That way your hajj will be more complete. And your umra will be more complete if you do it outside of the months of the hajj."

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 ‏.‏