After Allah affirms in this noble Surah that `Isa was a worshipper and servant of Allah and He mentioned his birth from Maryam without a father, He then begins refuting those who claim that He has a son. Holy is He and far Exalted is He above such description. Allah says,
(And they say: "The Most Gracious has begotten a son." Indeed you have brought forth) This means, "In this statement of yours."
شَيْئاً إِدّاً
(a thing Idda.) Ibn `Abbas, Mujahid, Qatadah and Malik all said, "Terrible." It has been said that it is pronounced Iddan, Addan, and Addan with elongation on the first vowel. All three of these pronunciations are known, but the most popular is the first. Allah said;
"And the mountains to fall down crumbling" - 19:90.
These verses suggest that the earth, the mountains and everything that grows thereon possess a certain degree of knowledge and intelligence though in their case these perceptions are not of the same extent as that bestowed on human beings. This explains the fact that everything in the world glorifies Allah Ta’ ala as will be evident from the verse.
وَإِن مِّن شَيْءٍ إِلَّا يُسَبِّحُ بِحَمْدِهِ
"Arid there is not a single thing that does not extol His purity and praise." - 17:44.
These verses refer to this very perception of these things that to associate anything or being with Allah Ta` ala, specially to assert that He has children is a sin which makes the earth and the mountains quake with fear. Sayyidna ` Abdullah Ibn ` Abbas ؓ has said that except humans every created thing is terrified of any suggestion of association with Allah (Ruh, -ul-Ma` ani).
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 87–91
When Truth in its authentic form appears before a man and still he ignores it, this disregard of his paves the way for Satan’s entry into his very soul. As a result, his mind is given over to obduracy. Now he is not able to accept any argument in a right and positive manner. God’s signs may appear in front of him, but he offers self-devised explanations for them and even uses them to bolster his rebellious attitude and his arrogance. One who assumes false supports to be his real supports, which he can safely lean on, falls a prey to the same foolishness time and again. But those who fear God consider God alone to be their real support. The fear of God makes the believers give no importance to such people as mislead others into the belief that they are their true support. Thus it is the believers alone who will be God’s guests of honour in the life hereafter.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.