A caravan was proceeding towards Mecca via Medina. They stopped in Medina for a few days and proceeded on their journey again.
On the way, a friend joined them. While individually greeting them, his eye fell on one person who was generously helping everyone with their chores. He recognized him instantly and asked the travellers if they knew who he was. They replied in the negative. ‘He joined us in Medina, but after these last few days of travelling together we can easily say that he is extremely pious, virtuous and God-fearing. We did not ask him, but he is always busy helping anyone who needs assistance in some way or the other.’ The friend of the travellers said, ‘I am sure you do not recognize him, for if you did, you would never allow him to do your petty chores.’ The travellers, stupefied, asked, ‘After all, who is he?’ ‘He is Ali ibn al Husain, Zain ul Abedin (‘a)’, he replied.
The entire caravan was overwhelmed with shame and regret for not enquiring who he was when he joined them. They rushed towards him to kiss the hands that had performed all those menial tasks for them. They complained, crying, ‘Why did you hide your identity? We could have committed an act of disrespect and never forgiven ourselves for it.’
The Imam (‘a) replied, ‘I intentionally joined your caravan because you did not know me. Whenever I travel with acquaintances, they treat me with great respect and affection because of my grandfather, the Holy Prophet (s), and do not permit me to do anything at all. I, therefore try to accompany people who do not recognize me, so that I can look after myself, do my own work, and without introducing myself, earn the pleasure of serving others.’
Reference : Anecdotes of The Ahlul Bayt (Daastaan e Raastaan ) by Ayatullah Murtadha Mutahhari