I notice you're asking for a download link to "Windows 7 Service Pack 3" — but I should clarify that Windows 7 Service Pack 3 does not exist. Microsoft ended mainstream support for Windows 7 in 2015 and extended support in 2020, with the last official service pack being SP1 (released in 2011).
Do not download ISOs from torrent sites or random Google Drive links. If the hash (SHA-1/MD5) does not match Microsoft’s official generic hashes, treat it as compromised.
There is no official Windows 7 Service Pack 3 (SP3). Microsoft only ever released one official service pack for Windows 7, which was Service Pack 1 (SP1).
Before you spend hours trying to download an "SP3 ISO," consider the reality of the situation.
While no official ISO exists for "SP3," you can download the original Windows 7 with SP1 or use community-developed "Convenience Rollups" that include all post-SP1 updates. Official Windows 7 Software (SP1)