Can you mention the reference for this narration?
الصيام جنة ما لم يخرقها صاحبها وخرقها الغيبة
This narration appears in Musannaf ‘Abdur Razzaq as the statement of Hafsah bintu Sirin (rahimahallah).
(Musannaf ‘Abdur Razzaq, Hadith: 7895)
The opening words; ‘Fasting is a shield’ also appear in Sahih Bukhari, Sahih Muslim and other Hadith collections.
(Sahih Bukhari, Hadith: 1894, 7492 and Sahih Muslim, Hadith: 1151)
Also see here.
Fasting will serve as a shield as long as a person does not breach it by engaging in backbiting.
And Allah Ta’ala Knows best.
Answered by: Moulana Suhail Motala
Approved by: Moulana Muhammad Abasoomar
Checked by: Moulana Haroon Abasoomar