Sunan an-Nasa'i, Volume 3, Book 24, Hadith 2648 (DarusSalam) ⓘ
It was narrated that Ibn 'Abbas said: "A woman lifted a child up to the Messenger of Allah and said: 'Is there Hajj for this one?' He said: 'Yes, and you will be rewarded.'''(sahih)
أَخْبَرَنَا عَمْرُو بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا أَبُو نُعَيْمٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ إِبْرَاهِيمَ بْنِ عُقْبَةَ، عَنْ كُرَيْبٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ رَفَعَتِ امْرَأَةٌ إِلَى النَّبِيِّ صلى الله عليه وسلم صَبِيًّا فَقَالَتْ أَلِهَذَا حَجٌّ قَالَ " نَعَمْ وَلَكِ أَجْرٌ " .
also referenced under: Hadith 2647 (Reference) & Book 24, Hadith 0 (In-Book)