Wajibs are acts that are required and that complete the performance of a prayer. Those who accidentally omit, forget, or delay the performance of a wajib act must perform a prostration of forgetfulness (Sajdat al-Sahw).
Some of the Wajibs of a prayer are as follow:
1- Reciting the Chapter of the Opening (Surah al-Fatiha).
2- Reciting after the Surah al-Fatiha, an additional chapter or at least three verses.
3- Reciting the Surah al-Fatiha before the additional surah.
4- Placing the nose on the ground on prostration (al-Sajdah).
5- Reciting of the supplication of witnessing (at-tahiyyatu) in the sitting (qa’da) in the second rakah for the three and four-rakah prayers.
6- Performing all of the pillars of the prayer perfectly. In other words, one should not hurry, and perform the standing (al-Qiyam), bowing (al-Ruku), prostrating (al-Sujud), and sitting (al-Qa’da) properly. For example, those who go into prostration (al-Sajdah) before standing up straight and for a time long enough to recite “Rabbana laka al-hamd” after the bowing (al-Ruku) would omit heeding “ta’dil al-arkan,” that is, performance of all the pillars of the prayer peacefully and at ease.
7- Reciting of the supplication of witnessing (at-tahiyyatu) in each of the first and final sittings.
8- Reciting an extra al-Takbir (Allahu Akbar), and reciting the supplication of Qunut in the Odd-Numbered Prayer (Salat al-Witr).
9- After the completion of the prayer reciting the salutation (As-Salam) to the right side and to the left side.
10- Making the prostration for forgetfulness (Sajdat al-Sahw) if any acts are mistakenly omitted in the ritual prayer.
11- Loud recitation of the Noble Quran by the prayer leader (Imam) in the prayers where this is prescribed, such as the Dawn Prayer (Salat al-Fajr), Sunset Prayer (Salat al-Maghrib), and the Night Prayer (Salat al-‘Isha).
12- The leader (Imam) reciting the Noble Quran silently in the prayers this is prescribed such as the Noon Prayer (Salat al-Zuhr) and the Late Afternoon Prayer (Salat al-Asr).
13- When performed congregation, the prayer leader (imam) reciting aloud the Fatiha and the additional surahs of the Noble Qur'an in the obligatory rakats of the Morning Prayer (Salat al-Fajr), in the first two rakats of the obligatory rakats of the Sunset Prayer (Salat al-Maghrib) and the Night Prayer (Salat al-Isha), in the friday Assembly Prayer (Salat jum'a), and in both the Festival Prayer (Eid Prayers)