Is it obligatory to place one's hands on the chest during prayer, and what should I do if my father orders me not to do that?

Placing the hands in prayer is a Sunnah (definition). The Shafi'is, Hanafis, and Hanbalis agree on the permissibility of grasping [the hands]. The Shafi'is permit placing them on the chest, while the Hanafis and Hanbalis believe they should be placed below the navel. As for the Malikis, their adopted view is to let them hang (irsal), but they have another narration that speaks of grasping them and placing them below the chest and above the navel. Obeying one's father takes precedence over performing this Sunnah. It is advisable to counsel him gently and explain the Ahadith narrated concerning this, among them the Hadith (definition) of Wa'il ibn Hujr that the Prophet, peace and blessings be upon him, used to grasp his left hand with his right, placing his right hand on the back of his left palm, the wrist, and the forearm, and on his chest.