It is reported from Qatadah (may Allah have mercy on him) regarding the saying of Allah Almighty, "Those who humble themselves in their prayers" [Surah al-Mu'minun: 2], that it means humility in the heart and keeping the gaze lowered.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3526
Hadith Gradingمحدثین:صحيح لغيره
Hadith Takhrij«صحيح لغيره۔ اخرجه الطبري في تفسيره 9/ 196»