Now the phrase “for they are given things in similitude (wa utū bihi mutashābihan):” this is a parenthetical clause confirming and explaining the previous one, and is a summary and appendix of it.
The use of the passive mood in “they are given” indicates that they are served.
While “in similitude” alludes to the combining of two pleasures as you already know.
The phrase “and they have therein companions pure (wa la-hum fī-hā azwājun muṭahharatun):” by virtue of the relationship between two sentences joined by a conjunction, the “and” [here] indicates that just as they are in need of dwellings for their bodies, so are they need a means of rest and tranquillity for their spirits.
“They have (la-hum)” indicates particularity and possession, and specifying and restriction, and infers that besides their wives of this world they shall have houris, created specially for them.
And “therein (fī-hā)” indicates that these wives will be worthy of Paradise and that their beauty will be proportionate to their elevated degree. Moreover, in this is a concealed sign that Paradise is adorned and decked out with them.
The word “pure (muṭahharatun)” indicates that someone has cleansed and purified them, but don’t suppose that anyone cleansed by the hand of power [can be described]! Its being a transitive verb [the IInd form] suggests that the women of this world are cleansed and purified so they become as beautiful as houris, who are of themselves pure.
And the phrase “and they abide therein for ever (wa hum fī-hā khālidūn)” indicates that both themselves, and their wives, and the delights of Paradise, and all of Paradise, are eternal.