During an investigation of allegations of corruption charges of Malaysian PM, investigators revealed evidence of Saudi interference in internal affairs of other Muslim countries.
It was discovered that the $681m (£479m) deposited in the bank account of Malaysian PM Najib Razak by Saudi Arabia was to help him win the 2013 elections, a Saudi source says.
Malaysia's attorney general cleared Mr Najib of allegations of corruption on Tuesday after ruling that the money was a donation from the Saudi royal family.
Mr Najib had denied that the money came from state-owned investment fund 1MDB.
The Saudi source said the donation was made amid concern in Riyadh about the influence of the Muslim Brotherhood.
At the time, Malaysia's opposition alliance included the Pan-Malaysian Islamic Party (PAS). Its founders were inspired by the Brotherhood, although there is little evidence the Brotherhood actually has much support in Malaysia.
Mr Najib's coalition went on to win the election, but with one of its poorest showings in more than 50 years in power.