What I saw was, when Bani was trying to convince Sahil to leave the rope, Baba was shouting something like, 'tumhe tumhari maa ki kasam hai Bani aisa mat karo'. Then afterwards when Bani wasn't listening to him he warned/threatened her that her mother will die, as in if you break the 'maa kasam' your mother will die. I understood this while watching then later on baba was going to clarify this with Manveer.
Cursing or wishing death upon someone is a different thing, which is more heinous according to me.
This stupid man has no right to give kasams and bring people's mothers and their lives for the sake of silly captaincy tasks. He should also stop his Tantar vidyas and jaaps for tasks. What's this big reason over loving Priyanka so much that he is ready to give so much of stress and trauma to other contestants?