Can a person during his lifetime write in his will that after my death my house or car will go to my son knowing that his son will get a share from his estate.
Bismillahi Ta’ala
Walaikum Assalam Warahmatullah
Nabi ﷺ has mentioned in his last sermon, as recorded in Sunan al-Tirmidhi that
“Indeed Allah has stipulate share for every rightful heirs, hence there is no bequest for an inheritor”
Since the son is an inheritor from the estate of deceased father, any bequest in his favor is invalid and batil.
However, if all the other heirs give permission after the demise of the father to give that portion to the bequeathed, then it will be treated as if they dropped their own right to the extent in that wealth.
Wallahu A’lam
And Allah Ta’āla Knows Best
Mufti Faisal al-Mahmudi