Knowledge about Allah,the Almighty and Majestic,
Knowlege about prophet Muhammad S.A.W
Knowledge about religion of Islam
It is not allowed to worship Allah with ignorance since whoever does this is astray.
Since person who has knowledge but does not implement it has evoked Allah's anger,as they have knowledge but did not act accordingly.
One of deceptive enticement of satan is that he discourags people from gaining benefecial knowledge by deceiving the person into thinking that he is excsed by Allah due to his ignorance.
What this person does not realize is the he deliberately stays away from learning while he has ability,the proof is established againts him (punishment).This is the trick of satan played upon people of Noah,as Allah S.W.T mentioned in Quran when they :"put their finger in their ears and covered themselves with their clothes"...
in order to plea that the proof would not be established againts them.
3.CALLING AND PROPAGATING TH KNOWLEDGE AND PRACTICE FOR ISLAM
Allah the Exalted cursed the Israelites because they used to forbade others the wickedness that they themselves would do,and what an evil thing they did.
Teaching and calling to Islam is a community of obligation,and thus when some of them fulfill this obligation none are blameworthy,but if all leave it,all are blameworthy.
4.HAVE PATIENT AND PRESEVERANCE with any misfortune faced in learning,practicing,teaching and calling others to it.