Don't think this is the right place to discuss about religious practice but to answer your question, raising of hands is a symbolic gesture of one trying to reach out to God and is commonly so in Christianity. Here's a quote in the Old Testament
1Kings 8:37-39*If there is a famine in the land, or plagues, or crop disease, or attacks of locusts or caterpillars, or if your peoples enemies are in the land besieging their townswhatever the trouble isand if your people offer a prayer concerning their troubles or sorrow,
raising their hands toward this Temple, then hear from heaven where you live, and forgive. Give your people whatever they deserve, for you alone know the human heart.
Note: the Temple here refers to the Temple in Jerusalem which was built in honour of God and for His Santuary and the Jews would come to offer their sacrifices and made their prayers during their time.
Is it written in the Holy Bible that Christians worship raising their hands??