Baba mentions his Guru didn't give him a mantra. How then does he explain the transmission of spiritual knowledge and grace?

Baba explicitly states in Chapter 19 that his Guru did not blow any mantra into his ears. He explains that the transmission of grace happens through a much more subtle and profound connection. He uses the analogy of a mother tortoise, who is on one bank of a river while her young are on the other, and she nurtures them solely through her loving glance. This sight alone brings happiness and contentment. Therefore, Baba suggests that the direct, attentive gaze and merciful glance of the Guru is how he himself was protected and nurtured, rendering the effort of a mantra unnecessary.