Tadabbur increases the faith
وَإِذَا مَا أُنزِلَتْ سُورَةٌ فَمِنْهُم مَّن يَقُولُ أَيُّكُمْ زَادَتْهُ هَٰذِهِ إِيمَانًا ۚ فَأَمَّا الَّذِينَ آمَنُوا فَزَادَتْهُمْ إِيمَانًا وَهُمْ يَسْتَبْشِرُونَ
And whenever a surah is revealed, there are among the hypocrites those who say, "Which of you has this increased faith?" As for those who believed, it has increased them in faith, while they are rejoicing. (Surah At Tawbah 124)
It brings Khashya (fearing Allah with knowledge), Khawf (Fear) and Rajaa' (Hope).
اللَّهُ نَزَّلَ أَحْسَنَ الْحَدِيثِ كِتَابًا مُّتَشَابِهًا مَّثَانِيَ تَقْشَعِرُّ مِنْهُ جُلُودُ الَّذِينَ يَخْشَوْنَ رَبَّهُمْ ثُمَّ تَلِينُ جُلُودُهُمْ وَقُلُوبُهُمْ إِلَىٰ ذِكْرِ اللَّهِ ۚ ذَٰلِكَ هُدَى اللَّهِ يَهْدِي بِهِ مَن يَشَاءُ ۚ وَمَن يُضْلِلِ اللَّهُ فَمَا لَهُ مِنْ هَادٍ
Allah has sent down the best statement: a consistent Book wherein is reiteration. The skins shiver therefrom of those who fear their Lord; then their skins and their hearts relax at the remembrance of Allah . That is the guidance of Allah by which He guides whom He wills. And one whom Allah leaves astray - for him there is no guide. (Surah Az Zumar 23)
Tadabbur leads to action
وَهَٰذَا كِتَابٌ أَنزَلْنَاهُ مُبَارَكٌ مُّصَدِّقُ الَّذِي بَيْنَ يَدَيْهِ وَلِتُنذِرَ أُمَّ الْقُرَىٰ وَمَنْ حَوْلَهَا ۚ وَالَّذِينَ يُؤْمِنُونَ بِالْآخِرَةِ يُؤْمِنُونَ بِهِ ۖ وَهُمْ عَلَىٰ صَلَاتِهِمْ يُحَافِظُونَ
And this (the Quran) is a blessed Book which We have sent down, confirming (the revelations) which came before it, so that you may warn the Mother of Towns (i.e. Makkah) and all those around it. Those who believe in the Hereafter believe in (the Quran), and they are constant in guarding their Salat (prayers). (Surah Al An'am 92)
Tadabbur takes you from..
..the level of eeman (faith) to the level of ihsaan (excellence).
..worries and calamities to relief and contentment of the heart.
..sadness and gloom to joy and happiness.
...tightness to vastness.
..the trap of desires to the sweetness of obedience & closeness.
..misguidance to guidance.
The Prophet (صلى الله عليه وسلم) said:
"Indeed, I have left among you, that which if you hold fast to it, you shall not go astray:
The Book of Allah.."
(Sahih Muslim)
Hold on to the Book, understand it, ponder upon it and act upon it.
The Prophet (صلى الله عليه وسلم) said:
The Qur'an is a proof for you or against you.
(Sahih Muslim 223)
Proof for you: if you take it to understand, ponder and act upon it.
Against you: if you turn away from it, do not learn it or act upon it.
The fruits and virtues of tadabbur are great. The one who ponders upon the Words of Allah will have faith in his heart, it helps him to act upon it and reach the Pleasure of Allah.