«فَتَوَجَّسَ مَا هَجَسَ فِي أَفْكَارِهِمْ وَفَطِنَ لِمَا بَطَنَ»
He sensed what troubled their thoughts and understood what remained hidden.
Tawajjasa is to sense or suspect quietly; hajasa to arise as an inner thought; faṭina to perceive cleverly; baṭana to remain concealed.
The connected expressions illustrate psychological alertness. His next response will address not just their words but also their hesitation.