Kindly mentioned some Hadiths with authenticity and reference for Isal thawab, especially regarding dhikr like the first kalimah or other adhkar which are recited for Isal thawab.
Answer:
In principle, Isal thawab can be done with any nafl ‘ibadah, be it nafl Salah, nafl fast, nafl haj or even dhikr or Quran recital.
See a detailed article, with the proofs you’ve requested here.
Kindly refer to a reliable Mufti/Darul ifta for more.
And Allah Ta’ala Knows best,
Answered by: Moulana Muhammad Abasoomar