Bakr bin 'Abdullah Al-Muzani said:

"Anas said: 'I heard the Prophet reciting the Talbiyah for 'Umrah and Hajj together. I told Ibn 'Umar about that and he said: "He recited the Talbiyah for Hajj only. I met Anas and told him what Ibn 'Umar had said, and Anas said: "do you think of us as no more than children? I heard the Messenger of Allah say: 'Labbaika 'Umratan wa Hajjan ma'an (Here I am (O allah) for 'Umrah and Hajj together) (sahih)

أَخْبَرَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا هُشَيْمٌ، قَالَ حَدَّثَنَا حُمَيْدٌ الطَّوِيلُ، قَالَ أَنْبَأَنَا بَكْرُ بْنُ عَبْدِ اللَّهِ الْمُزَنِيُّ، قَالَ سَمِعْتُ أَنَسًا، يُحَدِّثُ قَالَ سَمِعْتُ النَّبِيَّ ﷺ يُلَبِّي بِالْعُمْرَةِ وَالْحَجِّ جَمِيعًا فَحَدَّثْتُ بِذَلِكَ ابْنَ عُمَرَ فَقَالَ لَبَّى بِالْحَجِّ وَحْدَهُ . فَلَقِيتُ أَنَسًا فَحَدَّثْتُهُ بِقَوْلِ ابْنِ عُمَرَ فَقَالَ أَنَسٌ مَا تَعُدُّونَا إِلاَّ صِبْيَانًا سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ " لَبَّيْكَ عُمْرَةً وَحَجًّا مَعًا " .