Elder of the community under six Gurus; first custodian of the Adi Granth
Baba Buddha
A Jat boy named Bura who met Sri Guru Nanak Dev Ji while herding cattle and earned the name Buddha, the old one, for his gravity. He lived to 125 by the tradition, anointed five successive Gurus, was the first reader of the scripture in the Harmandir, and taught Sri Guru Hargobind Ji to fight.
Life
Bura was born in 1506 in a village near Amritsar. The tradition has him, aged about twelve, bring milk to Sri Guru Nanak Dev Ji and explain that he was anxious about death because he had seen soldiers cut down crops young and old alike. Sri Guru Nanak Dev Ji called him Buddha, an old man in a child, and the name stayed.
He went to Kartarpur, and after Sri Guru Nanak Dev Ji's passing became the senior figure around each Guru in turn. It was Buddha who applied the mark of succession to Sri Guru Angad Dev Ji, Sri Guru Amar Das Ji, Sri Guru Ram Das Ji, Sri Guru Arjun Dev Ji and Sri Guru Hargobind Ji. He supervised the digging of the pools at Amritsar and Tarn Taran, and when the Adi Granth was installed in the Harmandir in 1604 Sri Guru Arjun Dev Ji made him its first granthi, the reader and custodian.
Sri Guru Arjun Dev Ji entrusted Sri Guru Hargobind Ji's upbringing to him, and the martial training of the sixth Guru is credited to this very old man. He retired to farm Guru Ji's lands at Jhabal and passed away in 1631 at Ramdas, where Sri Guru Hargobind Ji came to perform the rites. A line of his descendants kept the office of custodian for generations.[EoS][EoS][EoS]
Images

A later fresco of Baba Buddha at Gurdwara Baba Bir Singh, labelled in Gurmukhi. Probably 19th century.
Unknown, Probably 19th century. Gurdwara Baba Bir Singh (as stated on Commons). Public domain. Source

A gilded panel from doors given to the Harmandir Sahib by Maharaja Ranjit Singh, now in the treasury according to Commons. It imagines Baba Buddha anointing Sri Guru Amar Das Ji under Sri Guru Angad Dev Ji's command.
Unknown, c. 1801-1839. Toshakhana, Harmandir Sahib (as stated on Commons). Public domain. Source