Surah Al-Mu'minun, Ayah 7

Which was Revealed in Makkah

بِسْمِ اللَّهِ الرَّحْمَـنِ الرَّحِيمِ

In the Name of Allah, the Most Gracious, the Most Merciful.

The Success is for the believers whose qualities are described here

قَدْ أَفْلَحَ الْمُؤْمِنُونَ

(Successful indeed are the believers) means, they have attained victory and are blessed, for they have succeeded. These are the believers who have the following characteristics:

الَّذِينَ هُمْ فِى صَلاَتِهِمْ خَـشِعُونَ

(Those who with their Salah are Khashi`un.) `Ali bin Abi Talhah reported that Ibn `Abbas said:

خَـشِعُونَ

"(Khashi`un) means those with fear and with tranquillity." This was also narrated from Mujahid, Al-Hasan, Qatadah and Az-Zuhri. It was reported from `Ali bin Abi Talib, may Allah be pleased with him, that Khushu` means the Khushu` of the heart. This was also the view of Ibrahim An-Nakha`i. Al-Hasan Al-Basri said, "Their Khushu` was in their hearts." So they lowered their gaze and were humble towards others. Khushu` in prayer is only attained by the one who has emptied his heart totally, who does not pay attention to anything else besides it, and who prefers it above all else. At that point it becomes a delight and a joy for eyes, as in the Hadith recorded by Imam Ahmad and An-Nasa'i from Anas, who said that the Messenger of Allah ﷺ said:

فَمَنِ ابْتَغَىٰ وَرَ‌اءَ ذَٰلِكَ فَأُولَـٰئِكَ هُمُ الْعَادُونَ (However, those who seek (sexual pleasure) beyond that are the transgressors - 7). Satisfying one's desire with someone other than one's own wife or a lawfully acquired slave-girl is strictly forbidden and the ban includes adultery (marrying a woman whom one is not allowed to marry under the religious code is also adultery), having sex with one's wife or slave-girl when she is menstruating or is confined, or having unnatural sex with them, homosexuality and bestiality, while most jurists include masturbation also in the ban. (Tafsir Bayan ul-Qur’ an, Qurtubi, al-Bahr ul-Muhit, etc.)