Recite what has been revealed to you of the Book, and perform the Ṣalāh. Verily, the Ṣalāh prevents from Al-Faḥshā’ (immoral sins) and Al-Munkar (evil deeds) and the remembering (praising) of Allāh is greater indeed. And Allāh knows what you do. (Surah Al-Ankabut 29. verse 45)

 

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Abu  Al-ʿĀliyah commented on the Āyah:

إِنَّ الصَّلَاةَ تَنْهَىٰ عَنِ الْفَحْشَاءِ وَالْمُنكَرِ ۗ

(Verily, the Ṣalāh prevents from immoral sins and evil wicked deeds)

Prayer has three attributes, and any prayer that contains none of these attributes is not truly prayer: 

Being done purely and sincerely for Allāh alone (Ikhlāṣ), fear of Allāh and remembrance of Allāh. Ikhlāṣ makes a person do good deeds, fear prevents him from doing evil deeds, and the remembrance of Allāh is the Qur’ān which contains commands and prohibitions.^[1]

^[1] Ibn Abi Ḥātim recorded this narration under this Āyah.

Source: Tafsir Ibn Kathir (Abridged) Volume 7, Sūrah 29. (45) Al-‘Ankabūt (Part-20), page. 494-495, Darussalam