A summary of the understanding held by the people of the Sunnah
regarding the meaning of the Qur'an being entirely mutashābih (consistent/similar), versus only some of its verses being mutashābih (ambiguous).
Allah Almighty said:
“Allah hath (now) revealed the fairest of statements, a Scripture consistent, (wherein promises of reward are) paired (with threats of punishment), whereat doth creep the flesh of those who fear their Lord, so that their flesh and their hearts soften to Allah's reminder. Such is Allah's guidance, wherewith He guideth whom He will. And him whom Allah sendeth astray, for him there is no guide.” (39:23)
"The skins of those who fear their Lord shiver from it."
This means that the entire Qur'an is mutually consistent in its excellence, perfection,
harmony, and complete absence of any contradiction whatsoever.
Even its most subtle and profound meanings—
whoever contemplates them becomes certain that they could only originate from One who is All-Wise, All-Knowing.
For this reason, the Qur'an has also been described as being entirely muhkam (clear and precise).
Allah Almighty said:
“Alif. Lam. Ra. (This is) a Scripture the revelations whereof are perfected and then expounded. (It cometh) from One Wise, Informed,” (11:1)
As for the saying of Allah Almighty:
“He it is Who hath revealed unto thee (Muhammad) the Scripture wherein are clear revelations - they are the substance of the Book - and others (which are) allegorical. But those in whose hearts is doubt pursue, forsooth, that which is allegorical seeking (to cause) dissension by seeking to explain it. None knoweth its explanation save Allah. And those who are of sound instruction say: We believe therein; the whole is from our Lord; but only men of understanding really heed.” (3:7)
"and others are ambiguous,"
what is meant by it is
that the meanings of certain verses of the Qur'an may seem unclear or ambiguous to the understanding of many people,
and this confusion is not dispelled
except by referring these conceptually ambiguous verses
back to the other clear, decisive verses on the very same subject.
Pursuing these ambiguous verses
without referring them back to the clear and decisive ones
is a way of stirring up discord among people through them,
and it is the practice of the people of deviance and misguidance.
Allah Almighty said:
“He it is Who hath revealed unto thee (Muhammad) the Scripture wherein are clear revelations - they are the substance of the Book - and others (which are) allegorical. But those in whose hearts is doubt pursue, forsooth, that which is allegorical seeking (to cause) dissension by seeking to explain it. None knoweth its explanation save Allah. And those who are of sound instruction say: We believe therein; the whole is from our Lord; but only men of understanding really heed.” (3:7)
"they pursue what is ambiguous in it, seeking discord and seeking its interpretation."