So let not their speech grieve you. Indeed, We know what they (36:76)

Almuntakhab Fi Tafsir Alquran Alkarim

Therefore, let not their vain and unreasonable discourse O Muhammed grieve you at heart. We do know what they converse secretly or whisper under their breath and what they suggest secretly to the mind and all that their breasts store of thoughts and feelings. And We are well acquainted with all that they utter loudly and with all that is being said

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(36:76) Let not their words grieve you. Surely We know all things about them, what they conceal and what they reveal. *63

So let not their speech grieve you. Indeed, We know what they meaning

*63) The address is to the Holy Prophet. Here the allusion is to the campaign of vilification which the chiefs of the disbelievers of Makkah were carrying on against him. They knew in their hearts and acknowledged in their private assemblies that the charges they brought against him were absolutely baseless. In order to create suspicions against him in the minds of the people, they branded him a poet, sorcerer, magician, madman, etc. But their consciences recognized, and they also acknowledged before one another, that whatever they were uttering Was false, which they were forging only to frustrate his mission. That is why Allah says to His Prophet: "Do not grieve at their absurd and meaningless talk. Those who are opposing and resisting the Truth with falsehood shall ultimately meet with failure in this world and see their evil end in the Hereafter, too. "
 

So let not their speech grieve you. Indeed, We know what they meaning in Urdu

اچھا، جو باتیں یہ بنا رہے ہیں وہ تمہیں رنجیدہ نہ کریں، اِن کی چھپی اور کھلی سب باتوں کو ہم جانتے ہیں