Is there a text or hadith that mentions the virtue of saying: "I have believed in Allah the Almighty, and disbelieved in Al-Jibt and At-Taghut, and I have grasped the most trustworthy handhold which shall not break, and Allah is All-Hearing, All-Knowing"?

This remembrance has no authentic chain of transmission. Its narration comes from 'Arafah bin Yazid al-'Abdi, who is unknown in status and narrated a denigrated hadith (definition). Furthermore, there is a discrepancy in identifying the Companion to whom this remembrance is attributed (Urwah bin al-Mughirah or Urwah bin al-Zubayr), and the report is unproven due to the presence of unknown narrators in its chain. However, there is no harm in saying this remembrance occasionally, or in adopting it as a private Ruqyah (definition) (spiritual healing). Yet, it should not be considered a fixed Sunnah (definition), as the recommendation to regularly recite a specific remembrance requires a legal proof.