Bonaventure — on Rev 7:2 (Collations on the Hexaemeron, Collation 16)

“And it is certain that one of them wanted to exterminate the Church. But an "angel ascending from the rising of the sun cried to the four angels: 'Do not harm the earth or the sea till we have sealed the servants of our God on their foreheads.'" Wherefore the Church's tribulations are lasting until now.”