The affix gha comes in the sense of 'like' after the word sahasra in the Instrumental -3rd case in construction, in the chandas (Vedas).,
The case of construction is indicated by the sutra. Thus सहस्रेण संमितः = सहस्रियः 'like unto thousand'. As in the following verse:- सहस्रिथासोऽपां नोर्मयः ॥ अयमग्निः सहस्रियः The word संमित means तुल्य 'equal to'. Some read the word समित instead of सम्मित, but the meaning will be the same.,