With accent marks:
Свя́то ме́сто пу́сто не быва́ет.
A holy place is never empty.
If a good place is empty, someone else immediately takes it.
For example, a position promising benefits and tempting prospects is rarely vacant - there are always those who want to take it.
Other Russian proverbs
The eyes are scared, but the hands are doing.
In a healthy body, healthy mind.
All is well that ends well.
A bird is visible by its flight.
To live a life is not the same (not as easy) as to go through a field.
A well-fed man does not understand a starving one.
Don't go to the woods if afraid of wolves.
The further into the forest, the more firewood is there.