And they say: "When this promise, if you are truthful? (71)Say: "Perhaps that which you wish to hasten on, may be close behind you. (72)Verily, your Lord is full of grace for mankind, yet most of them do not give thanks (73)And verily, your Lord knows what their breasts conceal and what they reveal (74)And there is nothing hidden in the heaven and the earth but it is in a Clear Book (75)

Allah tells us about how the idolators asked about the Day of Resurrection, but thought it unlikely that it would ever come to pass.

وَيَقُولُونَ مَتَىٰ هَٰذَا الْوَعْدُ إِنْ كُنْتُمْ صَادِقِينَ

(And they say: "When (will) this promise (be fulfilled), if you are truthful?")

Allah said, responding to them:

قُلْ 

(Say) 'O Muhammad,'

عَسَىٰ أَنْ يَكُونَ رَدِفَ لَكُمْ بَعْضُ الَّذِي تَسْتَعْجِلُونَ

(Perhaps that which you wish to hasten on, may be close behind you.)

Ibn 'Abbas said, "That which you wish to hasten on has come close to you, or some of it has come close." This was also the view of Mujahid, Ad-Dahhak, 'Ata Al-Khurasani, Qatadah and As-Suddi. This is also what is meant in the Ayat:

وَيَقُولُونَ مَتَىٰ هُوَ ۖ قُلْ عَسَىٰ أَنْ يَكُونَ قَرِيبًا 

(And they say: "When will that be?" Say: "Perhaps it is near!")(17:51)

يَسْتَعْجِلُونَكَ بِالْعَذَابِ وَإِنَّ جَهَنَّمَ لَمُحِيطَةٌ بِالْكَافِرِينَ 

(They ask you to hasten on the torment. And verily, Hell, of a surety, will encompass the disbelievers)(29:54).

عَسَىٰ أَنْ يَكُونَ رَدِفَ لَكُمْ

(may be close behind you.) means, it is being hastened for you. This was reported from Mujahid. Then Allah says:

وَإِنَّ رَبَّكَ لَذُو فَضْلٍ عَلَى النَّاسِ 

(Verily, your Lord is full of grace for mankind,) meaning, He abundantly bestows His blessings on them even though they wrong themselves, yet despite that they do not give thanks for those blessings, except for a few of them.

وَإِنَّ رَبَّكَ لَيَعْلَمُ مَا تُكِنُّ صُدُورُهُمْ وَمَا يُعْلِنُونَ 

(And verily, your Lord knows what their breasts conceal and what they reveal.) means, He knows what is hidden in their hearts just as He knows what is easily visible.

سَوَاءٌ مِنْكُمْ مَنْ أَسَرَّ الْقَوْلَ وَمَنْ جَهَرَ بِهِ 

(It is the same (to Him) whether any of you conceals his speech or declares it openly)(13:10),

يَعْلَمُ السِّرَّ وَأَخْفَى

(He knows the secret and that which is yet more hidden)(20:7),

أَلَا حِينَ يَسْتَغْشُونَ ثِيَابَهُمْ يَعْلَمُ مَا يُسِرُّونَ وَمَا يُعْلِنُونَ ۚ

(Surely, even when they cover themselves with their garments, He knows what they conceal and what they reveal)(11:5).

Then Allah tells us that He is the Knower of the unseen in the heavens and on earth, and that He is the Knower of the unseen and the seen, i.e., that which is unseen by His servants and that which they can see. And Allah says:

وَمَا مِنْ غَائِبَةٍ

(and there is nothing hidden) Ibn 'Abbas said, "This means, there is nothing

فِي السَّمَاءِ وَالْأَرْضِ إِلَّا فِي كِتَابٍ مُبِينٍ

(in the heaven and the earth but it is in a Clear Book.)

This is like the Ayah,

أَلَمْ تَعْلَمْ أَنَّ اللَّهَ يَعْلَمُ مَا فِي السَّمَاءِ وَالْأَرْضِ ۗ إِنَّ ذَٰلِكَ فِي كِتَابٍ ۚ إِنَّ ذَٰلِكَ عَلَى اللَّهِ يَسِيرٌ

(Know you not that Allah knows all that is in the heaven and on the earth Verily, it is (all) in the Book. Verily, that is easy for Allah.)(22:70)