Arcana Coelestia #9597
9597. 'With cherubs' means the Lord's watchfulness, guarding it from the approach of the hells and the harm they can do. This is clear from the meaning of 'cherubs' as watchfulness and providence, preventing any approach to the Lord except through good and protecting from harm the good from the Lord which exists in heaven and with man, dealt with in 9509, consequently guarding heaven from the approach of the hells and the harm they can do.
Isaiah 40:22
22
It is he that sitteth upon the circle of the earth, and the inhabitants thereof are as grasshoppers; that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in: