"The Knower of the unseen and the witnessed" (Al-Ghayb): the secret; "and the witnessed" (al-shahada): the manifest. "You will judge between Your servants," meaning: the believers and the polytheists. His judgment between them shall be that He admits the believers into Paradise and admits the polytheists into the Fire.
﴿عَالم الْغَيْب وَالشَّهَادَة﴾ الْغَيْب: السِّرّ , وَالشَّهَادَة: الْعَلَانِيَة ﴿أَنْتَ تحكم بَين عِبَادك﴾ يَعْنِي: الْمُؤمنِينَ وَالْمُشْرِكين؛ فَيكون حكمه بَينهم أَن يدْخل الْمُؤمنِينَ الْجنَّة وَيدخل الْمُشْركين النَّار.