薛道光（1078-1191），字式，号道源，陕西鸡足山人，以南宗三祖著称。《宝诰》中尊称为紫贤真人。他本是一僧，法名紫贤，因人称毗陵禅师。曾云游长安，在开福寺留学，与长老修岩、高僧如环等深交。一次偶然的观察桔槔之举，使他顿悟无上圆明真实法要，其机锋敏捷、宗说兼通，被视为六祖慧能悟性之后又一大成就者。
然而，他意识到个人智慧不足以探究金丹修命之秘传，因此开始寻访。在宋徽宗崇宁五年冬，他在眉县青镇的一座佛寺听讲时，遇到了八十高龄的石泰道人。这位神秘的石泰不仅黑发红颜，而且夜间还会做针线活计，显得非凡。薛道光通过引用张伯端诗句触及了他的底线，并向他请教《悟真篇》的内容。石泰见其诚心，就简要地为其揭示了大要。
薛道光听后大悟，一切疑团如同桶中的水一扫而空。他信服石泰是张紫阳的直传，便叩拜要求成为门下弟子。但石泰担忧有叛教之嫌，而薛道光坚定回答：“生死大事，不拘于门户，只怕自己耽误。”Stone was impressed and decided to pass on the true teachings, telling Salvo to seek out powerful patrons to support his practice. He then retired from the world, leaving Salvo to continue his journey.
From that day on, Salvo devoted himself fully to the Way of Internal Alchemy. He wrote several influential works, including "The Song of Danxi", "The Return of Danxi and the Mandate", and an annotated version of "The Awakening True Classic". His teachings spread far and wide, illuminating the path for countless seekers after truth.
In his later years, Salvo achieved enlightenment and passed away at the age of 114. Before he died, he left behind a poem that has become famous in its own right: "Iron horses gallop into the sea / Mud snakes fly up into heaven / The three islands of Penglai are not in the west."
