They are those who are certain that they are going to meet their Lord, and that unto Him they are going to return.
continues the subject that was started in the previous Ayah. Therefore, the prayer, or the advice to observe it is heavy,
إِلاَّ عَلَى الْخَاشِعِينَ
الَّذِينَ يَظُنُّونَ أَنَّهُم مُّلَقُو رَبِّهِمْ
(except for Al-Khashi`in. (They are those) who are certain (Yazunnuna) that they are going to meet their Lord), meaning, they know that they will be gathered and face their Lord on the Day of Resurrection,
وَأَنَّهُمْ إِلَيْهِ رَاجِعُونَ
(and that unto Him they are going to return), meaning, their affairs are all subject to His will and He justly decides what He wills.
Since they are certain that they will be returned to Allah and be reckoned, it is easy for them to perform the acts of obedience and refrain from the prohibitions.
Ibn Jarir commented on Allah's statement;
يَظُنُّونَ أَنَّهُم مُّلَقُو رَبِّهِم
(Yazunnuna that they are going to meet their Lord),
Ibn Jarir said; "The Arabs call certainty as well as doubt, Zann. There are similar instances in the Arabic language where a subject as well as its opposite share the same name. For instance, Allah said,
وَرَأَى الْمُجْرِمُونَ النَّارَ فَظَنُّواْ أَنَّهُمْ مُّوَاقِعُوهَا
And the Mujrimun (criminals, polytheists, sinners), shall see the Fire and Zannu (apprehend) that they have to fall therein." (18;53)
It is recorded in the Sahih that;
on the Day of Resurrection, Allah will say to a servant, "Have I not allowed you to marry, honored you, made the horses and camels subservient to you and allowed you to become a chief and a master?"
He will say, "Yes."
Allah will say, "Did you have Zann (think) that you will meet Me?"
He will say, "No."
Allah will say, "This Day, I will forget you, just as you forgot Me."
If Allah wills, we will further elaborate on this subject when we explain Allah's statement,
نَسُواْ اللّهَ فَنَسِيَهُمْ
(They have forgotten Allah, so He has forgotten them), (9;67)