Obligatory word prolongation, light

The mechanic

A madd letter inside a word followed immediately by a letter carrying a plain sukun rather than a shadda. It occurs in only two places in the whole mushaf: 10:51 and 10:91.

Where it occurs

Its condition, and its two places

ا و ي

• ٓU+0653
• ۡU+06E1

Length, as reported

Six harakat is what is reported, as with the other lazim types.

A place in the text

أَثُمَّ إِذَا مَا وَقَعَ ءَامَنتُم بِهِۦٓۚ ءَآلۡـَٰٔنَ وَقَدۡ كُنتُم بِهِۦ تَسۡتَعۡجِلُونَ

The marked spot was located in this ayah's own text at build time — Yunus 10:51.