And we verily gave unto Moses the Scripture, and there was strife thereupon; and had it not been for a Word that had already gone forth from thy Lord, the case would have been judged between them, and lo! they are in grave doubt concerning it.
“Here we have again the mystic doctrine of “the Word”. Cf. vi. 115, ix 40, and iv. 171. “Word” is the Decree of God, the expression of His Universal Will or Wisdom in a particular case. When men began to diverge from one another (see last note) God made their very differences subserve the higher ends by increasing their emulation in virtue and piety, and thus pointing back to the ultimate Unity and Reality.”
Yusuf Ali, Abdullah. Translation and Commentary of the Quran. (Surah 10 verse 19). Quran Arabic with English Translation & Commentary (Tafsir) by Abdullah Yusuf Ali, Free Download (quran4u.com)