Ibn 'Arabî points out (V, 148-49) that
"the divine knowledge received directly from God's Presence through revelation ('ilm ladunnî ilâhî mashrû') has a single taste - even if the places where it is drunk may differ, they do not differ in being good: and whether it is good or better, it is all pure, without any corruption... For the prophets and saints and everyone who informs us from God all say the same thing of God...not differing among themselves, and confirming one another - just as the pure rain from the sky is not different when it falls.
So let the foundation of your purification of your heart be with water like this - with nothing but knowledge known through divine revelation (shar'), which has been likened to rainwater. ... then your own essence and your purification (of it) will be like that spring from which water flows forth. And if you should differentiate sweetness or saltiness (in what is claimed to all be 'revealed' rainwater), then know that your perceptions are sound! This is a topic to which I have not found anyone alluding. And yet the person who eats sugar knows its sweetness like that, and knows that there is something wrong with the bitterness of aloes: they don't need a "rational proof" (dalîl 'aqlî) (to recognize the difference)! Now I have definitely pointed this out to you, so take my indication to heart - and watch out!
Now that that is established, my friend, start employing the forms of knowledge given by the revelation (shar') in (purifying) your own essence, and use the knowings of the saints and the true Knowers who took them from God in your own spiritual exercises and spiritual efforts and exertions, refraining from the excesses (i.e., the desires) of the bodily members and the promptings of the egoistic self (the nafs) For if you cannot distinguish between those waters (i.e., which are truly pure and divinely revealed, and which polluted by human interference), then know that something is wrong with your nature, that it has somehow been corrupted. In that case we can do nothing for you, except that God may help you, through His Lovingmercy."