Whosoever shall swear ... - See the notes at Matthew 5:33-37.
The temple - See the notes at Matthew 21:12.
It is nothing - It amounts to nothing - it is not binding.
The gold of the temple - Either the golden vessels in the temple - the candlestick, etc.; or the gold with which the doors and other parts of the temple were covered; or the gold in the treasury. This, it seems, they considered far more sacred than any other part of the temple, but it is not known why.
He is a debtor - He is bound to keep his oath. He is guilty if he violates it.