Invite to the way of your Lord with wisdom and good instruction, and argue with them in a way that is best. Indeed, your Lord is most knowing of who has strayed from His way, and He is most knowing of who is [rightly] guided.
Invite - O Messenger - to the religion of Islam, you and the believers who follow you, in a manner that is appropriate for the condition, understanding and mindset of the person who you are inviting and with admonition that contains encouragement and caution. Argue with them in the manner that is best in terms of speech, thought and politeness, for it is not your duty to guide people. You are only required to convey the message to them. Your Lord knows best who has strayed from the religion of Islam and He knows best those who are rightly guided to it, so do not lose yourself in grief over them.