Final answer:
Mata Sahib Kaur is known as the spiritual mother of all Sikhs, specifically those within the Khalsa, due to her significant role in its history and teachings.
Step-by-step explanation:
The spiritual mother of all Sikhs, specifically the Khalsa, is Mata Sahib Kaur. The title of spiritual mother was bestowed upon her by Guru Gobind Singh, the tenth Guru of Sikhism, who formed the Khalsa, a spiritual brotherhood and sisterhood devoted to purity of thought and action. Mata Sahib Kaur is revered for playing a pivotal role in the history and formation of the Khalsa and is often associated with the nurturing of the principles of Sikhism among its adherents.