"Those who ascribe rivals to God (al-adilun billah) cry lies when they make Him similar to the like of their categories, adorn Him in their imaginations with the adornment of creatures, divide Him with a measure resulting from the notions of their concerns, and measure Him by the talents of their reason's powers in terms of the creatures with their multiple faculties. For how should the deliberations of imaginations assess Him whose measure cannot be determined, when surely the notions of understanding have erred in conceiving of His inmost center ? For He is greater than that the minds of men should delimit Him through thought (tafkir) or angels should encompass Him through estimation, despite their proximity to the kingdom of His might."
High be He exalted above having an equal (kufw) with which to be compared, for He is the Subtle: when imaginations desire to encroach upon Him in the depths of the unseen regions of His dominion, (when) thoughts (fikar) free from insinuating intrusions seek to grasp knowledge of His Essence, (when) hearts are thrown into mad confusion over Him in trying to embrace Him through conforming to His attributes, (when) the ways of approach of reason's powers become obscured since no attributes attain to Him by which they might gain the knowledge of His divinity, (then) they (imaginations, thoughts, hearts and ways of approach) are checked in disgrace while traversing the chasms of the dark reaches of the unseen worlds, rid (of all things) for Him-glory be to Him!
They return having been thrown back, admitting that the inmost center of His knowledge is not reached through the deviation of straying (from the path)] and that no notion of the measure of His might's majesty occurs to the mind of meditators, by reason of His distance from being (encompassed) within the faculties of limited beings. For He is counter to (khilaf) His creation, and there is nothing like Him among creatures. Now a thing is only compared with its like (adil). As for what has no like, how should it be compared with what is other than its like (mithal) ? And He is the Beginning (al-badi) before whom was naught, and the Last (al-akhir) after whom will be naught."
Imam Ali (a.s.) on God's transcendence - translated by William Chittick in "A Shi'ite Anthology"