The Book of Pilgrimage
وَحَدَّثَنِيهِ زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا عَفَّانُ، حَدَّثَنَا هَمَّامٌ، حَدَّثَنَا قَتَادَةُ، بِهَذَا الإِسْنَادِ وَقَالَ فِي الْحَدِيثِ فَافْصِلُوا حَجَّكُمْ مِنْ عُمْرَتِكُمْ فَإِنَّهُ أَتَمُّ لِحَجِّكُمْ وَأَتَمُّ لِعُمْرَتِكُمْ .Qatada narrated this hadith with the same chain of transmitters saying:(That 'Umar also said): Separate your Hajj from 'Umra, for that is the most complete Hajj, and complete your Umra
From Sahih Muslim, whose reports the scholars accept as authentic.