:sl:
MashaAllaah..
The Lughah in which the "Am" replaces the Alif-laam is Himyariyyah /
حميرية spoken by the people of Himyar. This Lughah originated from Yemen after the kingdom of Saba' had fallen. And from what my teacher told me some people still speak it till this day.
However the Hadith (Hadith Jabir bin 'Abdillaah:
ليس من امبر امصيام في امسفر ) in this lafdh is weak, wallaahu a'lam.
There are other Shawaahid Shi'riyyah like the bayt;
و ان مولاي ذو يعاتبني *** لا احنة عنده و لاجرمه
ينصرني منك غير معتذر *** يرمي ورائي بامسهم و امسلمه
.