And if you asked them, "Who sends down rain from the sky and gives life thereby to the earth after its lifelessness?" they would surely say, "Allāh." Say, "Praise to Allāh"; but most of them do not reason.
Allah states that there is no God but He. The idolators who worshipped others besides Him recognized that He was the sole creator of the heavens and earth, the sun and the moon, alternating the night and day. They acknowledged that He was the Creator Who provided for His servants and decreed how long they should live. He made them and their provision different, so that some were rich and some were poor, and He knew best what was suitable for each of them, who deserved to be rich and who deserved to be poor. So, Allah stated that He has alone created everything, and that He alone is controlling them -- if this is how it is, then why worship anyone else Why put one's trust in anyone else Since dominion is His Alone, then let worship be for Him Alone. Allah often establishes His divinity by referring to their acknowledgement of His Unique Lordship, because the idolators used to acknowledge His Lordship, as they said in their Talbiyah (during Hajj and `Umrah: "At Your service, You have no partner, except the partner that You have, and You possess him and whatever he has."
Ma'arif al-Qur'an
Mufti Muhammad ShafiOn ayahs 61–63
After stating the real source of sustenance for all, that is the bounty of Allah Ta’ ala, it is said that if you ask the infidels as to who has created the earth and the skies, or who controls the movement of the sun and the moon, or who brings in the rain, and who makes the vegetation grow; then even they will admit that it is all controlled and done by One entity, that is Allah Ta’ ala. In the next sentence it is advised to ask them as to why do they then worship any other than Allah and regard it as their mentor. From the next verse وَلَئِن سَأَلْتَهُم مَّنْ خَلَقَ السَّمَاوَاتِ وَالْأَرْضَ (And if you ask them as to who has created the heavens and the earth - 29:61) until the end of the ruku` this subject continues.
Creating the earth and the sky was such a major event that only Almighty God could perform it. The movement of the sun and moon, the falling of rain and the sprouting of greenery from the soil of the earth are phenomena too great to have been brought into existence by anybody other than God. Those who indulge in polytheism do not themselves believe that they have brought these great wonders into existence. In spite of this, many people worship beings others than God in the hope that they will increase their worldly blessings. However, when all powers are vested in God, who else but He can exert influence on the distribution of the daily sustenance?
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.