And We have already sent messengers before you to their peoples, and they came to them with clear evidences; then We took retribution from those who committed crimes, and incumbent upon Us was support of the believers.
Here Allah mentions the favor He does for His creatures by sending winds to them, as harbingers of His mercy, meaning that they will be followed by rain. Allah says:
وَلِيُذِيقَكُمْ مِّن رَّحْمَتِهِ
(giving you a taste of His mercy,) that is, the rain which will come down and revive people and the land.
وَلِتَجْرِىَ الْفُلْكُ بِأَمْرِهِ
(and that the ships may sail at His command,) means, on the sea, for they are driven by the wind.
وَلِتَبْتَغُواْ مِن فَضْلِهِ
(and that you may seek of His bounty,) means, by trading, earning a living and traveling from one country to another, one region to another.
فَانتَقَمْنَا مِنَ الَّذِينَ أَجْرَمُوا وَكَانَ حَقًّا عَلَيْنَا نَصْرُ الْمُؤْمِنِينَ (Then We took vengeance upon those who were guilty. And it was due on Us to help the believers. -30:47). This verse tells us that Allah Ta’ ala has taken it upon Himself to help the believers. On the face of this statement, one would have expected that Muslims would never be defeated against the infidels. But on many occasions, results have been exactly opposite. Answer to this confusion is at hand in this very verse, that by the word 'believers' those believers are intended who fight with infidels purely for the sake of Allah. Allah Ta’ ala takes revenge of only such believers from the criminals and helps them overpower their adversaries. Wherever the position is different, it is due to some sort of slip on the part of the believers, as Qur'an itself has quoted about the battle of Uhud: إِنَّمَا اسْتَزَلَّهُمُ الشَّيْطَانُ بِبَعْضِ مَا كَسَبُوا (Shaitan had but made them slip for some of their deeds - 3:155). Even in such a situation, Allah Ta’ ala graces them with victory and upper hand, once they realize their fault, as it happened in the battle of Uhud. As for such people who are Muslims only by name and are habitual defiant and negligent of the teachings of Islam, and are not penitent even when the infidels gain upper hand, they are for sure not included in this promise of Allah Ta’ ala, and do not qualify for His help. Nonetheless, Allah Ta’ ala provides help by His grace on many occasions without any one deserving it. Therefore, it is always beneficial to beg for His mercy and hope for His help.
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 47–52
The blowing of a cool breeze before the start of the rains announces the fact that the God of this world is the most Kind and Merciful. Sailing across the seas is very important for the promotion of civilization. But, this is possible only when the winds blow within certain limits. Similarly, in the present age, the possibility of air-travel is dependent upon the fact that God has arranged to maintain a layer of air on the surface of the earth and given human beings the knowledge of aerodynamics needed to design air worthy plans. All these arrangements have been made with a view to ensuring that man lives in the world as a grateful subject of God. The prophets of God appeared in the world in order to draw the attention of the people to these facts. But, while some accepted them others rejected them. Then, God helped those who accepted them and destroyed the deniers. The same fate on a larger scale awaits these two categories of human beings in the life Hereafter.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.