Maalik ibn e Anas, the famous scholar of Medina, once accompanied Imam Jafar al- Sadiq (‘a) on the Hajj. On reaching Meeqat, they all dismounted, donned the Ahram, offered the required prayer, and mounted their camels, raising the slogan of the Hajjis,
‘Labbaik Allahumma Labbaik, laa Shareeka Laka Labbaik, Innal Hamda wan Ne’amata Laka wal Mulk, laa Shareeka Lak,’
when they found the Imam (‘a) in an exceptionally strange state. He was shivering and his voice choking with emotion, unable to pronounce the obligatory slogan of Hajj. Maalik came to him and said, ‘Ya ibn e Rasool Allah, try to repeat the words with us. You know it is obligatory.’ ‘O Ibn e Abi Aamir! I am scared to utter these words. Do you know what they mean? They mean to declare,
“My Lord, I am ready to present myself before You, and ready to submit to Your Will.”
How can I proclaim that I am ready to submit to His Will and then disobey? What will I do if Allah responds to my open declaration with, “la Labbaik”?’
Reference : Anecdotes of The Ahlul Bayt (Daastaan e Raastaan ) by Ayatullah Murtadha Mutahhari