The Prophet (peace and blessings be upon him) said:
"We have been commanded to say after the prayers 'Subhan Allah' (Glory be to Allah) thirty-three times, 'Alhamdulillah' (All praise is for Allah) thirty-three times, and 'Allahu Akbar' (Allah is the Greatest) thirty-four times."
Hadith Referenceصحیح الجامع الصغیر / حرف الألف / 1381
Hadith Gradingالألبانی:صحيح
Hadith Takhrij[طب] عن أبي الدرداء. مجمع الزوائد ١٠/١٠١ وفتح الباري ٢/٢٧٢: ن – ابن عمر.