Prayer: Placing Hands on Top of One Another
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1115
If a person wakes up from the act of performing sajdah and doubts whether he is in the last sajdah of the prayer or in sajdat al‑shukr, then, whether he knows he fell asleep intentionally or unintentionally, his prayer is considered valid and it is not necessary for him to repeat it.
Third: a person places his hands on top of one another with the intention of humility and respect. The prayer becoming invalid by this act is based on obligatory precaution; however, there is no doubt that this act is unlawful if performed with the intention that it is sanctioned in Islamic law.