Question: why should we avoid najis? what are the advantages and disadvantages? Also qoute quran ayats if necessary to prove ur answer.
Answer: Najis substances are blood, urine, pus, vomit and the like. I have never encountered anyone, until now, that needs to be convinced to avoid such substances. Even non-muslims tend to avoid them because of their smell, appearance and tendency to carry diseases. Anyway, Allah ordered Prophet Muhammad to purify his clothes for prayer "wa thiaabaka faTahhir" in suuratu-l-mudaththir. This is a basic proof in this matter, but there are many hadiths about how to purify clothes and other things from najis.
Farhana asked: Why do we choose Allah as our God? How should we have iman in Him and to what extent?
Answer: Allah is the Arabic name of the Creator of everything that exists. Only He deserves to be worshipped because everything else is created and sustained by Him.
To have iman in Allah is to believe that He exists and that He is only attributed with complete perfection. This means that His attributes are not like that of created things. He is not limited in any way. He is one without a parter, part, child, or like. This belief is not a matter of extent; one either believes or one does not. If one believes without a doubt, then one is a Muslim, whereas if one has a fragment of doubt, then one is a non-muslim.
Take a look at the following articles:
The Islamic Belief in God: an explanation to fresh converts and non-Muslims
The Foundations of the Religion
Also click here to get a list of other articles.