URL Redirection

you can use HTTP::redirect.

HTTP::redirect wiki

https://devcentral.f5.com/wiki/iRules.http__redirect.ashx

e.g.

root@(ve11a)(cfg-sync In Sync)(Active)(/Common)(tmos) list ltm virtual bar
ltm virtual bar {
    destination 172.28.20.15:443
    ip-protocol tcp
    mask 255.255.255.255
    profiles {
        clientssl {
            context clientside
        }
        http { }
        tcp { }
    }
    rules {
        myrule
    }
    source 0.0.0.0/0
    vs-index 25
}

root@(ve11a)(cfg-sync In Sync)(Active)(/Common)(tmos) list ltm rule myrule
ltm rule myrule {
    when HTTP_REQUEST {
  if { [HTTP::uri] equals "/" } {
    HTTP::redirect "https://abc.com"
  }
}
}

[root@ve11a:Active:In Sync] config  curl -Ik https://172.28.20.15
HTTP/1.0 302 Found
Location: https://abc.com
Server: BigIP
Connection: Keep-Alive
Content-Length: 0