How does «مَا مَسَّهَا مِنْ نَقَبٍ وَلَا دَبَرٍ» relate to «أَقْسَمَ بِاللَّهِ أَبُو حَفْصٍ عُمَرُ»?

Faṣl: Substitution, Quasi-Complete Connection and Quasi-Complete Disjunction

• It begins a completely unrelated subject
• It introduces a vocative instead of an oath
• It specifies the content of the oath, answering the question raised by the first clause
• It negates the first hemistich and cancels the oath