"1. Assuredly, the exposition of Yoga, or Concentration, is now to be made. The Sanskrit particle atha, which is translated "assuredly," intimates to the disciple that a distinct topic is to be expounded, demands his attention, and also serves as a benediction. Monier Williams says it is "an auspicious and inceptive participle often not easily expressed in English.""
January 1, 1970
https://en.wikiquote.org/wiki/Yoga_Sutras_of_Patanjali