From Sahih Bukhari (Hadith 7343):
Narrated `Umar:The Prophet (ﷺ) said to me, "Someone came to me tonight from my Lord while I was in the 'Aqiq (valley), and said to me, "Offer prayer in this blessed valley and say: 'Labbaik' for the (performance of) `Umra and Hajj
Reference: Bukhari 7343