Tablet of Ahmad — Paragraph 10
Source (Arabic)
وَكُنْ كَشُعْلَةِ ٱلْنَّارِ لِأَعْدَائِي وَكَوْثَرِ ٱلْبَقَاءِ لِأَحِبَّائِي وَلَا تَكُنْ مِنَ ٱلْمُمْتَرِينَ
Translation
Be thou as a flame of fire to My enemies and a river of life eternal to My loved ones, and be not of those who doubt.