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."
قَالَ افْصِلُوا بَيْنَ حَجِّكُمْ وَعُمْرَتِكُمْ فَإِنَّ ذَلِكَ أَتَمُّ لِحَجِّ أَحَدِكُمْ وَأَتَمُّ لِعُمْرَتِهِ أَنْ يَعْتَمِرَ فِي غَيْرِ أَشْهُرِ الْحَجِّ
(That 'Umar also said): Separate your Hajj from 'Umra, for that is the most complete Hajj, and complete your Umra.
وَقَالَ فِي الْحَدِيثِ فَافْصِلُوا حَجَّكُمْ مِنْ عُمْرَتِكُمْ فَإِنَّهُ أَتَمُّ لِحَجِّكُمْ وَأَتَمُّ لِعُمْرَتِكُمْ
[Machine] To translate this passage into English, it says: "To differentiate between the pilgrimage (hajj) and the minor pilgrimage (umrah) and to perform the umrah outside the months of hajj is better for the completion of one's pilgrimage and the completion of their umrah."
أَنْ تَفْصِلُوا بَيْنَ الْحَجِّ وَالْعُمْرَةِ وَتَجْعَلُوا الْعُمْرَةَ فِي غَيْرِ أَشْهُرِ الْحَجِّ أَتَمُّ لِحَجِّ أَحدِكُمْ وَأَتَمُّ لِعُمْرَتِهِ