Is it permissible to face the Hijr during prayer, considering it a part of the Kaaba?

The majority of scholars hold that the prayer of one who faces only the Hijr without the Kaaba is invalid. This is because its status as part of the House (Kaaba) is conjectured, not certain, and therefore it is not sufficient for the qibla (definition) as a precautionary measure. However, the Hanbalis and Al-Lakhmi from the Malikis permit prayer facing the Hijr, basing their argument on the hadith (definition): "The Hijr is part of the House." They estimate its extent to be six cubits and a fraction, so whoever faces beyond that, their prayer is not valid.