The present study investigates the heat and mass transfer of magnetohydrodynamic (MHD) free convection through two infinite plates embedded with porous materials. In addition to that the combined effect of viscous dissipation, heat source/sink considered in energy equation and thermodiffusion effect is taken care of in the mass transfer equation. Using suitable non-dimensional variables, the expressions for the velocity, temperature, species concentration fields, as well as shear stress coefficient at the plate, rate of heat and mass transfer, i.e. Nusselt number (Nu) and Sherwood number (Sh) are expressed in the non-dimensional form. These coupled nonlinear differential equations are solved using perturbation technique and their behaviour is demonstrated via graphs for various values of pertinent physical parameters namely, Hartmann number (Ha), Reynolds number (Re), Schmidt number (Sc), Soret number (So), permeability parameter etc. In a particular case, the present result was compared with earlier established results and the results are found to be in good agreement. However, major findings are elaborated in the results and discussion section.