Allah accepts Repentance and responds to Supplications
Here Allah reminds His servants that He accepts repentance. If they turn to Him and come back to Him, then by His kindness and generosity He forgives, overlooks and conceals (their sins), as He says:
(And whoever does evil or wrongs himself but afterwards seeks Allah's forgiveness, he will find Allah Oft-Forgiving, Most Merciful.) (4:110) It was reported in Sahih Muslim that Anas bin Malik, may Allah be pleased with him, said, "The Messenger of Allah ﷺ said:
وَهُوَ الَّذِي يُنَزِّلُ الْغَيْثَ مِن بَعْدِ مَا قَنَطُوا (And He is the One who sends down rain after they have lost hope - 42:28) ". It is usual for Allah Almighty to send down rain whenever the earth is in severe need of water. But by saying "after they have lost hope", attention is being drawn towards the fact that sometimes Allah Almighty, in deviation from His usual norm, delays sending down rain so much that people begin losing hope. Apart from trial, such a happening is to warn that rain and famine are all in the power of Allah Ta’ ala; whenever He wants, He stops rain because of people's misdeeds, etc., so that people turn their attention towards His kindness, and display their humility and dependence. If rains had been subject to a strict time-table without any deviation, people would have considered rains to be purely subject to apparent causes, and would have become inattentive to Allah's Almighty's power. Here losing hope means losing hope in their contrivances because disappointment with Allah's kindness is kufr (infidelity).
Tazkirul Quran
Maulana Wahiduddin Khan
Human life on earth depends on water, but the supply of water is completely in God’s hands. If God does not provide water, man cannot obtain it on his own. Similarly, the distribution of sustenance is at the will of God. While doing so, God takes into account the depth of the human soul and, according to this, allocates sustenance to everybody. If people are given greater abundance than they can deal with with equanimity, they will become obstreperous and arrogant and, as a result, oppression and disturbance will prevail everywhere on the earth.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.