Religious obligations in Islam which are obligatory are divided between fard ‘ayn , duties incumbent upon each individual and fard kifayah, those incumbent on the community as a whole.
Fard `Ayn; is an act that is obligatory on every individual such as praying and fasting and he will be sinful if he does not do that.
There are numerous examples of Individual Obligations or Fard Ayn in Islam. Some of them are:
1. All Individual acts of Worship such as Salah, Fasting, Zakah, Hajj, etc
2. Islamic Knowledge: Some Islamic knowledge is obligatory for every accountable individual to learn. This is called fard ‘ayn (individual obligation). The definition is: if it has to do with an act of worship that he is obliged to do, or a transaction that he wants to engage in (then he must learn it).
3. Prayer in congregation is obligatory for healthy men in the mosque, according to the more correct scholarly opinion.
4. Returning the greeting of salaam is obligatory if the greeting is given to one person.
5. With regard to accepting invitations, if the invitation is to a wedding feast, then the majority of scholars are of the view that it is obligatory to accept unless there is a legitimate shar‘i reason not to do so.
6. Saying Yarhamuk Allah is an individual obligation upon everyone who hears the one who sneezed say Al-hamdu Lillah.