I remember a story where Baba asked Kaka Mahajani for money but not his companion. What was Baba's reason for excluding the friend?

You are referring to a powerful incident from Chapter 35 of the Shri Sai Satcharita. Kaka Mahajani's skeptical friend accompanied him to Shirdi, and while Baba asked Kaka for Dakshina on two separate occasions, He pointedly did not ask the friend. This caused the friend to feel restless and question why he was being excluded. When the friend was encouraged to ask Baba directly if he, too, should offer Dakshina, Baba gave a very clear reason for His earlier omission: "In your mind, there was no intent to give; Therefore, I did not ask you." This reveals that Baba's actions were a mirror to the devotee's own inner state; He would not compel an offering from someone who was not mentally and spiritually ready to give.