Sahih Muslim , Book 7, Hadith 3093 (USC-MSA) ⓘ
Karaib reported: A woman lifted a child and said: Messenger of Allah, would he be credited with Hajj? He said: Yes. and for you there would be a reward.
وَحَدَّثَنِي مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الرَّحْمَنِ، حَدَّثَنَا سُفْيَانُ، عَنْ إِبْرَاهِيمَ بْنِ عُقْبَةَ، عَنْ كُرَيْبٍ، أَنَّ امْرَأَةً، رَفَعَتْ صَبِيًّا فَقَالَتْ يَا رَسُولَ اللَّهِ أَلِهَذَا حَجٌّ قَالَ " نَعَمْ وَلَكِ أَجْرٌ " .
also referenced under: Book 15, Hadith 459 (In-Book) & Hadith 1336 (Reference)