Is it true that the prayer of one whose garment trails on the ground is not accepted, based on the fact that the Prophet, may Allah bless him and grant him peace, commanded a man to return and pray again because his garment was trailing?

Scholars have differed on the ruling of placing the hands after rising from rukūʿ (bowing). The preponderant view is that placing the hands on the chest is not legislated; rather, the hands remain by one's sides, or the worshipper places his right hand over his left.

As for the hadith: “When he (peace be upon him) rose from rukūʿ, he would raise his hands to the level of his shoulders until every bone returned to its place while standing, then he would let his hands hang down.” This hadith is weak and not authentic.

The jurists have stipulated that letting the hands hang down is recommended, and this is the madhhab of the Shāfiʿīs and the Ḥanbalīs.

Al-Nawawī said: "So when he raises his head from rukūʿ and stands upright, it is recommended to let his hands hang down without dispute. The evidence for this is that nothing has been authentically reported regarding placing the right hand over the left in this standing position, and the absence of evidence for something is proof of its absence."

Al-Buhūtī said: "And when he rises from his bowing, he stands upright, and he lets his hands hang down on his thighs, or on his chest."

Ibn Qudāmah said in Al-Mughnī: "And when he raises his head from rukūʿ and raises his hands, then when he stands upright, he lets his hands hang down. If he is in an odd rakʿah of his prayer, or he stands for the second, third, or fourth rakʿah, he places his right hand over his left."

In summary: The Sunnah is to let the hands hang down after rising from rukūʿ, whether it is in an obligatory or supererogatory prayer, and whether it is the first rakʿah or otherwise.

As for placing the hands on the chest, it is not legislated and there is no evidence for it.