Holy Quran

Allah purifies whom He pleases,

A man’s wrong belief does not in any way detract from the glory of God, but a belief in false deities lowers the dignity of man.

Man is made to rule nature itself and all creatures, but when he lowers himself before creatures lower than himself whom he was really made to rule, he sets at naught the very purpose of his creation.

It should be noted that shirk or setting up gods with God does not only mean idol-worship or worship of the forces of nature or a belief in the Divinity of mortals, but also includes the blind obedience which is rendered to great men; see 9:31a and also the next footnote.

The second form of punishment is their being overtaken by the curse which overtook the Sabbath-breakers,

whoever sets up a partner with Allah, he devises indeed a great sin.a

Shirk or setting up partners with Allah is spoken of as the gravest sin.

And Allah best knows your enemies. And Allah is sufficient as a Friend and Allah is sufficient as a Helper.

but Allah has cursed them on account of their disbelief, so they believe not but a little.

When water is not found, or is likely to do harm, tayammum suffices instead of ablution before prayer.