• رَّادِفَة
• رَدِفَ
• مُرْدِفِين

Appears 3 times in the Quran.

1. 8:9 إِذْ تَسْتَغِيثُونَ رَبَّكُمْ فَٱسْتَجَابَ لَكُمْ أَنِّى مُمِدُّكُم بِأَلْفٍ مِّنَ ٱلْمَلَٰٓئِكَةِ مُرْدِفِينَ

   When you sought aid from your Lord, so He answered you: I will assist you with a thousand of the angels following one another.
   

2. 27:72 قُلْ عَسَىٰٓ أَن يَكُونَ رَدِفَ لَكُم بَعْضُ ٱلَّذِى تَسْتَعْجِلُونَ

   Say: Maybe there may have drawn near to you somewhat of that which you seek to hasten on.
   

3. 79:7 تَتْبَعُهَا ٱلرَّادِفَةُ

   What must happen afterwards shall follow it.