Assalamu alaikum.i read a book some days ago about Dua and I saw one specific dua which I should repeat for 21 days and I was able to make just 8 days of it so my question is must I complet the remaining days or should I ignore it.your answer is important please Assalamu alaikum.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

The Thikr (remembrances of Allaah), Tasbeeh (glorifications), Istighfaar (seeking forgiveness) and supplications that Allaah The Almighty has prescribed are of two types:

1. Those whose virtue is associated with a specific number. Concerning them, one should fulfill and confine oneself to this number. An example is the Tasbeeh, Tahmeed, Takbeer and Tahleel after the five obligatory prayers, and some morning and evening remembrances of Allaah which are restricted to a specific number.

2. The general remembrance of Allaah, like the Tasbeeh, Istighfaar, supplication and the like which one can say at any time. It is not permissible to confine oneself to a specific number of it as this resembles imposition of religion.

After investigation, we have not come across an authentic supplication that should be repeated for twenty-one days, so confining oneself to it and adopting it as a Sunnah (tradition) is not permissible and it is considered as Bid'ah Idhaafiyyah (additional or secondary innovation, i.e. an act of worship whose basis is permitted but it contradicts the Sharee'ah regarding its reason, type, amount, manner, time or place). Hence, you should not continue saying it especially since you are incapable of doing so.  For more benefit, please refer to Fatwa 196517.

Therefore, we advise you to adhere to the supplications that are confirmed in the Book of Allaah and the authentic Sunnah, because they are sufficient and blessed.

Allaah Knows best.