Silsilat al-Ahadith al-Sahihah

Sayyiduna Ka'b bin 'Ujrah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "There are some words to be recited after every obligatory prayer; the one who says or does them will not be disappointed, and they are: thirty-three times «سبحان الله», thirty-three times «الحمد لله», and thirty-four times «الله اكبر»."