Imam Sadiq (as) was inquired,
When is the Day of ‘Hasrat’ i.e. regret?
The Day of Regret for which the Almighty Allah has warned.
Imam (as) replied, it is the Day of Judgment.
A Day, wherein the vitreous will also regret as to why they did not do better.
He further asked, will anyone not regret?
Imam (as) replied, Yes, one who continuously recited salawaat in this world.
اَللّٰهُمَّ صَلِّ عَلیٰ مُحَمَّدٍ وَ آلِ مُحَمَّدٍ
O Allah, send salutations upon Muhammad and the progeny of Muhammad
Reference
Wasail al-Shia, vol 7
My Salaams to My Imam in an Envelope of Noor.