When Guru Nanak Dev Ji reached Sialkot via Jammu he found the whole city in the grip of terror. Guru Dev Ji inquired and learnt that someone had failed to keep his promise made to a great saint called Hazrat Hamza Ghaus. He had flown into a rage and made a vow to meditate for 40 days and at the completion of his meditation the whole city would be doomed. Hearing this Sat Gur sat down under a Bair tree close to the place where Hazrat Hamza was meditating and sang his verse in a loud tone. It disturbed the maditation of Hamza Ji, who came to Guru Nanak and angrily asked who he was and why he wanted to save those liars. Guru Ji replied "Hamza, you are not supposed to punish a whole city for the misconduct of a single person." Hamza Ji was not satisfied. Guru Ji then explained to him that there were many souls. in the city who understood the purpose of life. Guru Ji gave two paisas to Bhai Mardana to buy "falsehood" and "truth" from the market. Some people ridiculed Mardana Ji but there was a Karar (a Hindu sect) named Maula who took two paisas and wrote two chits. On one chit he wrote, "Life is bitter" while on the other chit he wrote, "Death is truth". Bhai Mardana presented both the chits to Sat Gur Nanak Dev Ji. Guru Ji handed over the two pieces of paper to Hamza Ghaus Ji who after reading the same, pardoned the residents of Sialkot.
Maula Karar remained with Guru for some time during his travels. According to Guru'sbiographies, once Guru Ji went to fetch Maula Karar. He, at the instance of his wife, hid himself inside the dark portion of his house and his wife told Guru Dev Ji that he was not at home. Guru Ji came back and a little later it was learnt that Maula Karar had died of snake bite in the darkness.
The site where Guru Nanak Ji stayed is still called "Baba Bair". A beautiful and grand Gurdwara has been built at the site. The Bair tree under which Guru Dev Ji had stayed is still present. A few years back a grave of a Muslim fakir has been constructed under the tree.
Shaheed Natha Singh Ji had built this beautiful Shrine with great love and affection. Gian Singh Ji wrote his "History of Khalsa" while staying with the Mahant of this Gurdwara. The Shaheed Gang of Shaheed Natha Singh is within the precinct of the Gurdwara.
A big well was also constructed by him inside this Gurdwara and many Persian wheels worked in it. A beautiful tank was also there. Estate worth Rs 8000 belonging to Natha Singh Ji is now in the name of Gurdwara. which includes a garden, a pool and residential rooms. Two squares of land endowed to it is in district Layyalpur (Faisalabad). This sacred place had to suffer great damage in the wake of Babari Masjid dispute. There used to be a very high temple which was razed to ground when it was demolished by an unruly mob. The Gurdwara is in urgent need of repairs.