medieval cristians were not against all lending. Templars lent to governments as a way to raise funds. Regine Pernaud tells about a Bishop intervening to expel from the  land a farmer who did not pay his debts. Generally proto-banks existed in small scale. Kings borrowed $ to go to war. BUT:

* coins were gold or silver. No inflation risk. You lend 10 coins, if you receive back 10 coins after 1 year, you have only lost oportunity cost. It is very different from lending 10 dolars to get 10 dolars back after 1 year - who knows how much the dollar will be worth then?

* oportunity cost was generally lower than today (slower and less diverse economy, smaller population, diffcult transportation, etc.) 

* there were acceptable rates, Pernaud again tells about 3% to 7% / year depending on where/who/when. 

And lenders charging more, (~10-15%) would be considered usurers. With some reason given the above points. 

Albeit... some agitation or even violent events against usurers (not only Jews) appear to have been instigated by people who borrowed and did not pay... 

in renassaince times all shame is lost... 1519 imperial election was a borrowing orgy.. the candidates were bribing the electors. And it was larger but not the first time electors were bribed. 
To expel the Dutch from Brazil in 1650, Portugal got indebted for generations...

 

 Thank you for sharing this, I don't know much about it I recently started looking into it. It's very interesting. 

 another point about the middle ages: 
precious metal  was relatively scarce (obviously, how much depends on where/when) and a good part of the economy worked on produce - tipically serfs would pay in produce. 

A village could have only a handful of coins - the coins would circulate among them - whoever did not have the 'token' at the moment would have to trade produce or services. 

Thus, lending and borrowing would happen among people who dealt with larger amounts  - lords, merchants, or maybe the eventual larger scale farmer - e.g., a serf married a serf heiress, then his son got a double sized farm, and so on, eventually he has to hire people. 
So, dont expect "Joe the smallest serf" borrowing often, even small quantities.