Chullin 92 - Why Did The Angel Need to Go?
" Let me leave!" said [the stranger]. "Dawn is breaking. " "Are you thief or a kidnapper, who fears dawn?" - asked Jacob. "I am an angel, and since my creation my turn to sing a song to God has not arrived, till now, so I don't want to miss it," - answered the angel. That is why Jacob then asked for a blessing.
We see from here that some angels sing a song to God only once in a lifetime. Even those that do it daily can only sing their song after the prayers are said on earth. Moreover, angels mention the name of God only after three words, "Holy, holy, holy (is) God of Multitudes," whereas people say "Listen, Israel, God... Is One," mentioning the name of God after two words.
Earlier we mentioned that the prohibition of sciatic sinew does not apply to fowl because they lack the spoon-shaped flesh over the thighbone. But we see that they do!? - Yes, there is a spoon, but it is not round. Rabbi Yirmiyah inquired, "What if some bird does have a round spoon-shaped flesh?" - Inquiry unresolved.
Art: Giorgio da Castelfranco Veneto ( Giorgione) - The Singing Lesson