The phrase "evening star withdraws" is a poetic way of saying that the planet Venus, which is often called the evening star, sets below the horizon.

Here's a breakdown of what happens:

* Venus's Position: Venus orbits the sun closer than Earth. This means that sometimes Venus appears in the evening sky after sunset and sometimes it appears in the morning sky before sunrise.

* Evening Star: When Venus appears in the evening sky, it's referred to as the evening star. It shines brightly because it reflects sunlight.

* Withdrawal: As the Earth rotates, Venus appears to sink lower in the sky until it eventually sets below the horizon. This is the "withdrawal" of the evening star.

* Afterward: After Venus sets, the night sky will continue to darken until the moon rises or the stars become more visible.

The "withdrawal" of the evening star is a natural phenomenon caused by the relative positions of Earth, Venus, and the sun. It's a beautiful reminder of the constant motion and changes that occur in our solar system.