Which sound correspondence reinforces «فلا تقهر» and «فلا تنهر»?

Qalb, Tashrīʿ and Luzūm Mā Lā Yalzam: Completing the Verbal Ornaments

• Their initial consonants differ
• Both require qāf
• Both share final rāʾ and preceding hāʾ
• All letters are reversible