Manners and Customs of the Bible, 116. The Outstretched Hand
Article from https://bibletruthpublishers.com/bible-truth-study-bible/btsb
Exodus 10:21. The Lord said unto Moses, Stretch out thine hand toward heaven.
This is the custom of the Indian magicians when they deliver their predictions. It is done to show that they have favor with their gods.