After Allah stated that He created the heavens and earth and that He is the Owner and Possessor of the affairs Who makes things subservient (for mankind), He ordained that He be invoked in Du`a', for He is able to do all things. Allah also stated that He is the Sustainer and He resurrects the dead on the Day of Resurrection. Here, Allah said that He sends the wind that spreads the clouds that are laden with rain. Allah said in another Ayah,
وَمِنْ ءَايَـتِهِ أَن يُرْسِلَ الرِّيَـحَ مُبَشِّرَتٍ
(And among His signs is this, that He sends the winds with glad tidings) 30:46. Allah's statement,
بَيْنَ يَدَىْ رَحْمَتِهِ
(going before His mercy) means, before the rain. Allah also said;
وَهُوَ الَّذِى يُنَزِّلُ الْغَيْثَ مِن بَعْدِ مَا قَنَطُواْ وَيَنشُرُ رَحْمَتَهُ وَهُوَ الْوَلِىُّ الْحَمِيدُ
(And He it is Who sends down the rain after they have despaired, and spreads His mercy. And He is Al-Wali (the Guardian), Al-Hamid (the praiseworthy) 42:28 and,
فَانظُرْ إِلَى ءَاثَـرِ رَحْمَةِ اللَّهِ كَيْفَ يُحْىِ الاٌّرْضَ بَعْدَ مَوْتِهَآ إِنَّ ذَلِكَ لَمُحْىِ الْمَوْتَى وَهُوَ عَلَى كُلِّ شَىْءٍ قَدِيرٌ
(Look then at the results of Allah's mercy, how He revives the earth after its death. Verily, that is the one Who shall indeed raise the dead, and He is able to do all things) 30:50. Allah said next,
حَتَّى إِذَآ أَقَلَّتْ سَحَابًا ثِقَالاً
(Till when they have carried a heavy-laden cloud) when the wind carries clouds that are heavy with rain, and this is why these clouds are heavy, close to the earth, and their color is dark. Allah's statement,
سُقْنَـهُ لِبَلَدٍ مَّيِّتٍ
(We drive it to a land that is dead) that is, a dry land that does not have any vegetation. This Ayah is similar to another Ayah,
وَءَايَةٌ لَّهُمُ الاٌّرْضُ الْمَيْتَةُ أَحْيَيْنَـهَا
(And a sign for them is the dead land. We give it life) 36:33. This is why Allah said here,
فَأَخْرَجْنَا بِهِ مِن كُلِّ الثَّمَرَتِ كَذَلِكَ نُخْرِجُ الْموْتَى
(Then We produce every kind of fruit therewith. Similarly, We shall raise up the dead.) meaning, just as We bring life to dead land, We shall raise up the dead on the Day of Resurrection, after they have disintegrated. Allah will send down rain from the sky and the rain will pour on the earth for forty days. The corpses will then be brought up in their graves, just as the seeds become grow in the ground (on receiving rain). Allah often mentions this similarity in the Qur'an when He gives the example of what will happen on the Day of Resurrection, and bringing life to dead land,
لَعَلَّكُمْ تَذَكَّرُونَ
(so that you may remember or take heed.) Allah's statement,
وَالْبَلَدُ الطَّيِّبُ يَخْرُجُ نَبَاتُهُ بِإِذْنِ رَبِّهِ
(The vegetation of a good land comes forth (easily) by the permission of its Lord;) meaning, the good land produces its vegetation rapidly and proficiently. Allah said in another Ayah (about Maryam, mother of `Isa, peace be upon him);
وَأَنبَتَهَا نَبَاتًا حَسَنًا
(He made her grow in a good manner.) 3:37 The Ayah continues,
وَالَّذِى خَبُثَ لاَ يَخْرُجُ إِلاَّ نَكِدًا
(and that which is bad, brings forth nothing but with difficulty.) Mujahid, and others such as As-Sibakh, etc. also said this. Al-Bukhari recorded that Abu Musa said that the Messenger of Allah ﷺ said,
«مَثَلُ مَا بَعَثَنِي اللهُ بِهِ مِنَ الْعِلْمِ وَالْهُدَى كَمَثَلِ الْغَيْثِ الْكَثِيرِ أَصَابَ أَرْضًا فَكَانَتْ مِنْهَا نَقِيَّةٌ قَبِلَتِ الْمَاءَ فَأَنْبَتَتِ الْكَلَأَ وَالْعُشْبَ الْكَثِيرَ وَكَانَتْ مِنْهَا أَجَادِبُ أَمْسَكَتِ الْمَاءَ فَنَفَعَ اللهُ بِهَا النَّاسَ فَشَرِبُوا وَسَقَوْا وَزَرَعُوا وَأَصَابَ مِنْهَا طَائِفَةً أُخْرَى إِنَّمَا هِيَ قِيعَانٌ لَا تُمْسِكُ مَاءً وَلَا تُنْبِتُ كَلَأً، فَذَلِكَ مَثَلُ مَنْ فَقُهَ فِي دِينِ اللهِ وَنَفَعَهُ مَا بَعَثَنِي اللهُ بِهِ فَعَلِمَ وَعَلَّمَ وَمَثَلُ مَنْ لَمْ يَرْفَعْ بِذَلِكَ رَأْسًا وَلَمْ يَقْبَلْ هُدَى اللهِ الَّذِي أُرْسِلْتُ بِه»
(The parable of the guidance and knowledge with which Allah has sent me is that of an abundant rain falling on a land, some of which was fertile soil that absorbed rain water and brought forth vegetation and grass in abundance. And another portion of it was hard and held the rain water; and Allah benefited the people with it, they utilized it for drinking, making their animals drink from it, and for irrigation of the land for cultivation. And a portion of it was barren which could neither hold the water nor bring forth vegetation. The first is the example of the person who comprehends Allah's religion and gets benefit which Allah sent me with, by learnign and teaching others. The last example is that of a person who does not care for it and does not accept the guidance Allah sent me with.)