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
Each sandpiper praises its swamp.
Bitter truth is better than sweet lies.
We don't appreciate what we have but we cry when we lose it.
The demon is not as scary as he is depicted.
Put your trust in God, but don't make mistakes yourself
Living with wolves means to howl like a wolf.
Do not look at a given horse's teeth.
Your own shirt is closer to your body.