وَيَسْتَجِيبُ الَّذِينَ امَنُوا وَعَمِلُوا الصَّالِحَاتِ
...
And He answers those who believe and do righteous good deeds,
As-Suddi said, "This means, He responds to them."
This was also the view of Ibn Jarir:
"It means that He answers their supplication for themselves, their companions and their brothers."
...
وَيَزِيدُهُم مِّن فَضْلِهِ
...
and gives them increase of His bounty.
means, He answers their supplications and gives them more besides.
Qatadah said, narrating from Ibrahim An-Nakha`i Al-Lakhmi about the Ayah:
وَيَسْتَجِيبُ الَّذِينَ امَنُوا وَعَمِلُوا الصَّالِحَاتِ
(And He answers those who believe and do righteous good deeds,) --
(this means) they intercede for their brothers;
وَيَزِيدُهُم مِّن فَضْلِهِ
(and gives them increase of His bounty.) --
(this means) they intercede for their brothers' brothers.
...
وَالْكَافِرُونَ لَهُمْ عَذَابٌ شَدِيدٌ
And as for the disbelievers, theirs will be a severe torment.
-- having mentioned the believers and the great reward that is theirs, Allah then mentions the disbelievers and the severe, painful, agonizing torment that they will find with Him on the Day of Resurrection, the Day when they are brought to account.
The Reason why Provision is not Increased
Allah says here,