  We decompose the tribaryon configuration in terms of SU(3) flavor and spin
state and analyse their color-spin-flavor wave function following Pauli
principle. By comparing the color-color and color-spin interactions of compact
tribaryon configuration against the lowest three nucleon threshold within a
constituent quark model, we show that the three nucleon forces have to be
repulsive at short distance for all possible quantum numbers and all values of
the SU(3) symmetry breaking parameter. Our work identifies the origin of the
repulsive nuclear three body forces including the hyperons at short distance
that are called for from phenomenological considerations starting from nuclear
matter to the maximum mass of a neutron star.
