the soil is yet to be given, then the dead body should be taken out for funeral Ṣalāĥ and buried again. There is no specific number of days for offering the funeral Ṣalāĥ in front of the grave. The variation in duration depends on various factors, such as weather, type of soil, type/condition of the dead body and its disease. The body decays quickly in summer and in winter it takes longer, quickly in wet or salty soil, and slowly in dried or unsalted soil. Similarly an obese body decays faster than the skinny one. (Durr-e-Mukhtār, Rad-dul-Muḥtār, vol. 3, pp.134)
If a person died after falling into a well, or a house/building collapsed on him and the body cannot be recovered, his funeral Ṣalāĥ should be offered at the same place where he was deemed to be and if one is drowned in a river and his body could not be recovered then his funeral Ṣalāĥ cannot be offered as it is unknown whether the Muṣallī (Ṣalāĥ offering person is in front of him (the dead body) or not. (Rad-dul-Muḥtār, vol. 3, pp. 147)
If a person dies on the day of Jumu’aĥ, his funeral procession should be finished before Ṣalāt-ul-Jumu’aĥ if it is possible to do so. Delaying the funeral Ṣalāĥ just to have more participants after Jumu’aĥ is Makrūĥ.
(Baĥār-e-Sharī’at, vol. 1, pp. 830; Rad-dul-Muḥtār, vol. 3, pp. 173, etc.)