فَكَيْفَ تُنْكِـرُ حُبًّا^م بَعْدَمَا شَـهِدَتْ     بِهِ عَلَيْـكَ عُدُوْلُ الدَّمْعِ وَالسَّـقَمِ

6/6. So, how can you deny love while two trustworthy witnesses: (continuous) shedding tears and illness have testified against you regarding your love?

Since the claimant is denying love despite proof being available, the defendant severely criticizes him:
How can you deny love after I have brought clear proof against you? Your tears and sickness have testified to your love.

Question: How can love for Rasulullaah SallAllaahu Alayhi Wasallam be referred to as a sickness? This is supposed to be the highest level of perfection and good health.

Answer:

a.)  This is not a spiritual sickness. However bodily weakness is like a sickness.

b.) Sickness refers to restlessness waiting to meet the beloved. The person in love remains restless to meet his beloved.

1.) Sa‘eed ibn Abdul Azeez narrates that when Bilaal RadhiAllaahu Anhu was passing away, he exclaimed,

غَداً نَلْقَى الأَحِبَّهْ ... مُحَمَّداً وَحِزْبَهْ

I will tomorrow meet those whom I love, Muhammad SallAllaahu Alayhi Wasallam and his companions!

The wife of Bilaal RadhiAllaahu Anhum then said, وَاوَيْلاَهُ “How great my grief (at losing you)!”
To which Bilaal RadhiAllaahu Anhu replied, وَافَرَحَاهُ  “How great my happiness (at meeting Rasulullaah SallAllaahu Alayhi Wasallam and the Sahaabah)!”
(Siyar A‘laam min Nubalaa vol. 1 page 359)

2.) Abdah, the daughter of Khaalid Rahimahullaah, said, “Whenever he retired to bed, my father would stay awake thinking of Rasulullaah SallAllaahu Alayhi Wasallam with love and fondness. He would also remember every member of the emigrants (muhaajireen) and the helpers (ansaar) by name and say, “They were my seniors and my juniors and my heart yearns to meet them. O Allaah! Take my life soon so that I am able to meet them.” He would continue in this manner until he was finally overtaken by sleep.”
(Hilyatul-Awliyaa vol. 5 page 210 no. 430, Taareekh Dimishq vol. 16 page 199)

3.) During the Battle of Siffeen, Ammaar RadhiAllaahu Anhu said,

الْيَوْمَ أَلْقَى الْأَحِبَّةَ مُحَمَّدًا وَحِزْبَهُ، لَقَدْ قَاتَلْتُ بِهَذِهِ الرَّايَةِ ثَلَاثًا مَعَ رَسُولِ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ، وَهَذِهِ الرَّابِعَةُ

Today, I will meet the beloved ones, Muhammad and his companions. I had fought with this flag thrice with Rasulullaah SallAllaahu Alayhi Wasallam and this is the fourth.
(Bazzaar no. 1410)

Another narration states that Ammaar RadhiAllaahu Anhu called out during the Battle of Siffeen on the day he was martyred, “I have encountered oppressive people, I have married the beautiful wide-eyed damsels of Jannah. Today I will meet the beloved ones, Muhammad and his companions. Rasulullaah SallAllaahu Alayhi Wasallam had informed me that the final drink of my life in this world would be milk.”
(Al-Mu’jamul-Awsat of Tabaraani no. 6471)