Private conversation is only from Satan that he may grieve those who have believed,1 but he will not harm them at all except by permission of Allāh. And upon Allāh let the believers rely.
Translation: Saheeh International (English)
1 The reference may be to the sinful type of conversation, as mentioned in the previous verses, or to the practice of two persons speaking in confidence in the presence of a third, which might lead him to assume that he is the subject of their conversation. Such behavior was prohibited by the Prophet (ﷺ) in narrations of al-Bukhārī and Muslim.
فَلۡيَتَوَكَّلِlet put (their) trustfalyatawakkali
ٱلۡمُؤۡمِنُونَthe believersl-mu'minūna
Tafsir
Secret discussions that contain sin, inciting enmity and disobedience to the Messenger are only the result of Satan adorning and whispering to his associates, so that he can cause grief to the believers that they are being plotted against. However, neither Satan nor his beautification of things will harm the believers in any way, except if Allah wills and intends it. So it is upon Allah that the believers should rely in all their affairs.