Robbing Peter to pay Paul

Shifting resources around in order to be able to pay all debts/bills

e.g. I lent my sister £50 a few months ago but this week I don’t have enough to pay my car insurance. I can manage if I get the money back from my sister and don’t repay my mother the £100 I owe her until my next payday. Talk about robbing Peter to pay Paul.

Apparently the origin of the idiom relates to before the Reformation in Europe when a tax would be payable to both St Paul’s Church (London) and St Peter’s Church (Rome). Originally it appears to have referred to not paying the Peter tax to pay the Paul tax.
English folklore has it that the phrase alludes to an event in mid-16th century England in which the abbey church of Saint Peter, Westminster was deemed a cathedral but ten years later it was absorbed into the diocese of London when the diocese of Westminster was dissolved. A few years after that many of its assets were expropriated for repairs to Saint Paul's Cathedral.
Hence robbing Peter to pay Paul.