I heard Messenger of Allah ﷺ as saying: The invoker of curse would neither be witness nor intercessor on the Day of Resurrection.

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ إِنَّ اللَّعَّانِينَ لاَ يَكُونُونَ شُهَدَاءَ وَلاَ شُفَعَاءَ يَوْمَ الْقِيَامَةِ