إِنَّ اللَّهَ مَعَ الَّذِينَ اتَّقَوا وَّالَّذِينَ هُم مُّحْسِنُونَ

This verse indicates the character traits to be displayed by the dayee while facing up to his opponents. However, God says that if he is too sorely afflicted—allowing for human weakness in him as in other mortals, he is permitted to repay his tormentors in kind. But strictly speaking, the dayee is supposed to exercise patience whenever his addressees create trouble for him. Instead of adopting a retaliatory approach, he should leave all such issues to God. If the addressee does not accept the Truth, being bent rather on destroying the dayee and his mission, then the best course to be adopted by him is that of patience, i.e. avoiding reaction or retaliatory actions, he should continue conveying the message of Truth in a positive manner. The missionary has really to prove that, in fact, he is always conscious of God. If he proves this, then thereafter in all other matters, God becomes sufficient for him. After that no device of his opponents can harm him. However, strong his opponents may be. There are two kinds of human beings in this world. One is entirely focused on man and his activities, while the other is entirely focused on God. The latter see the powers of God with their own eyes. The former is never able to have control over impatience and anger. It is only the second type of person who can bear complaints and suffer bitterness and, for the sake of whatever he is going to receive from God, ignore whatever is meted out to him by his fellow men. The dayee must not have a vengeful mentality, and must abstain from retaliatory action. The conspiracies and devices of his opponents are likely to make him afraid that they may completely derail the call of Truth and destroy the preacher himself. But whatever the circumstances, he has to rely on God; he is required to have the firm belief that God sees everything and that He will support the Truth and defeat the falsehood.

— Source: Tazkirul Quran (Maulana Wahiduddin Khan) via Quran.com (16:128)