Ka'b bin 'Ujra reported Allah's Messenger (ﷺ) as saying: There are certain ejaculations, the repeaters of which or the performers of which after every prescribed prayer will never be caused disappointment: "Glory be to Allah" thirty-three times. "Praise be to Allah" thirty-three times, and "Allah is most Great" thirty-four times.
Hadith Referenceصحيح مسلم / كتاب المساجد ومواضع الصلاة / 596
'A'isha reported Allah's Apostle (ﷺ) saying: If a company of Muslims numbering one hundred pray over a dead person, all of them interceding for him, their intercession for him will be accepted.