( وَإِذَا لَمْ تَأْتِهِم بِآيَةٍ ) (And when you, [O Muhammad], do not bring them a sign): The speech is directed to our Prophet Muhammad (saws). (Sign) refers to a miraculous event, whether it be a cosmic sign or a Quranic verse. The Quranic verses serve as miraculous indications affirming the truthful Message delivered by the Prophet (saws) about Allah (swt). Cosmic signs include everything we witness, such as the sun, moon, stars, galaxies, air, water, clouds, plants, and animals, all serving as signs pointing to the existence of Allah (swt). Allah (swt) says:

 إِنَّ فِي خَلْقِ السَّمَاوَاتِ وَالْأَرْضِ وَاخْتِلَافِ اللَّيْلِ وَالنَّهَارِ وَالْفُلْكِ الَّتِي تَجْرِي فِي الْبَحْرِ بِمَا يَنفَعُ النَّاسَ وَمَا أَنزَلَ اللَّهُ مِنَ السَّمَاءِ مِن مَّاءٍ فَأَحْيَا بِهِ الْأَرْضَ بَعْدَ مَوْتِهَا وَبَثَّ فِيهَا مِن كُلِّ دَابَّةٍ وَتَصْرِيفِ الرِّيَاحِ وَالسَّحَابِ الْمُسَخَّرِ بَيْنَ السَّمَاءِ وَالْأَرْضِ لَآيَاتٍ لِّقَوْمٍ يَعْقِلُونَ

(Indeed, in the creation of the heavens and earth, and the alternation of the night and the day, and the [great] ships which sail through the sea with that which benefits people, and what Allah has sent down from the heavens of rain, giving life thereby to the earth after its lifelessness and dispersing therein every [kind of] moving creature, and [His] directing of the winds and the clouds controlled between the heaven and the earth are signs for a people who use reason.) (Al-Baqara: 164)

Meaning signs that indicate the existence of Allah (swt), but they want the sign to match what they want:

 ( 90 ) وَقَالُوا لَن نُّؤْمِنَ لَكَ حَتَّىٰ تَفْجُرَ لَنَا مِنَ الْأَرْضِ يَنبُوعًا ( 91 ) أَوْ تَكُونَ لَكَ جَنَّةٌ مِّن نَّخِيلٍ وَعِنَبٍ فَتُفَجِّرَ الْأَنْهَارَ خِلَالَهَا تَفْجِيرًا ( 92 ) أَوْ تُسْقِطَ السَّمَاءَ كَمَا زَعَمْتَ عَلَيْنَا كِسَفًا أَوْ تَأْتِيَ بِاللَّهِ وَالْمَلَائِكَةِ قَبِيلًا ( 93 ) أَوْ يَكُونَ لَكَ بَيْتٌ مِّن زُخْرُفٍ أَوْ تَرْقَىٰ فِي السَّمَاءِ وَلَن نُّؤْمِنَ لِرُقِيِّكَ حَتَّىٰ تُنَزِّلَ عَلَيْنَا كِتَابًا نَّقْرَؤُهُ ۗ قُلْ سُبْحَانَ رَبِّي هَلْ كُنتُ إِلَّا بَشَرًا رَّسُولًا

(( 90 ) And they say, “We will not believe you until you break open for us from the ground a spring. ( 91 ) Or [until] you have a garden of palm tress and grapes and make rivers gush forth within them in force [and abundance] ( 92 ) Or you make the heaven fall upon us in fragments as you have claimed or you bring Allah and the angels before [us] ( 93 ) Or you have a house of gold or you ascend into the sky. And [even then], we will not believe in your ascension until you bring down to us a book we may read.” Say, “Exalted is my Lord! Was I ever but a human messenger?”) (Al-Israa)

( قُلْ إِنَّمَا أَتَّبِعُ مَا يُوحَىٰ إِلَيَّ مِن رَّبِّي ) (Say, “I only follow what is revealed to me from my Lord): The issue is not about presenting a miracle whenever people may desire it to be; rather, miracles come from Allah (swt), and we follow the guidance received from the divine revelation of Allah (swt).

( هَٰذَا بَصَائِرُ مِن رَّبِّكُمْ) (This [Qur’an] is enlightenment from your Lord): (Enlightenment) refers to the illumination of spiritual matters, and the Holy Quran is an illumination in the heart and soul.

( وَهُدًى وَرَحْمَةٌ لِّقَوْمٍ يُؤْمِنُونَ ) (and guidance and mercy for a people who believe): It is guidance and blessings for human beings. Mercy is the most generous kind of giving. Allah (swt) says:

  وَنُنَزِّلُ مِنَ الْقُرْآنِ مَا هُوَ شِفَاءٌ وَرَحْمَةٌ لِّلْمُؤْمِنِينَ

(And We send down of the Qur’an that which is healing and mercy for the believers) (Al-Israa: 82)

Healing from any spiritual illness and it is mercy for the believers—constant and never-ending. Therefore, there are three aspects: insights, guidance, and mercy. If people seek a sign, the signs are illuminations and gifts from Allah (swt), providing insights, guidance, and mercy to those who believe in Allah (swt).