Hawk, Salam
قَدْ أَفْلَحَ الْمُؤْمِنُونَ
Indeed the following of those who identify their selves as Believers have attained perpetual success and fruitfulness: [23:01]
الَّذِينَ هُمْ فِي صَلَاتِهِمْ خَاشِعُونَ
Those who demonstrate solemnity and humble-mindedness in the performance of their As-Salaat: time bound Protocol of Servitude and Allegiance; [23:02]
Believer: Whoever pronounces making it public that he believes in Allah the Exalted, Qur'aan, Injeel before it and all the Books of Allah revealed in time line; all the Messengers of Him, the Angels and the Last Day.
They all are not declared successful. The characteristics of those claimants of belief who succeeded are given by Relative Pronoun الَّذِينَ.
The first element of success is performance of Salat. The successful are the true believers. Others are believers by tongue and lips. Kaafir is one who denies to have faith in aforementioned realities.
See who are truly the believers:
إِنَّمَا الْمُؤْمِنُونَ الَّذِينَ إِذَا ذُكِرَ اللّهُ وَجِلَتْ قُلُوبُهُمْ وَإِذَا تُلِيَتْ عَلَيْهِمْ آيَاتُهُ زَادَتْهُمْ إِيمَانًا وَعَلَى رَبِّهِمْ يَتَوَكَّلُونَ
الَّذِينَ يُقِيمُونَ الصَّلاَةَ وَمِمَّا رَزَقْنَاهُمْ يُنفِقُونَ
أُوْلَـئِكَ هُمُ الْمُؤْمِنُونَ حَقًّا
Take note; Truly the Believers are only those whose hearts blenched when Allah the Exalted is mentioned;
And when Aa'ya'at: the Verbal Passages of the Book of Him: Grand Qur'aan are recited to them word by word: Each Ayah: Unitary Verbal Passage gave them enhancement; the enhancement and conviction of belief.
And they have trust and hope in their Sustainer Lord. [8:02]
And they steadfastly maintain the Institution of As-sa'laat: Time Bound Formal Protocol of demonstrating Servitude and allegiance to Allah the Exalted.
Further, they heartily spend part of the worldly resources for other's welfare which We have given to them as sustenance. [8:03]
The aforementioned are the proven and established believers amongst claimants of belief.