Is it permissible for a worshipper to interrupt his prayer after the first tashahhud to do something and then complete it within a short period?

The basic rule is that it is forbidden for a worshiper to intentionally interrupt their prayer. However, it is permissible to interrupt it out of necessity, such as saving a life from perishing or securing property. It may even be obligatory in some cases, like aiding someone in distress or rescuing a drowning person. Interrupting an obligatory act of worship without a valid legal reason is not permissible, as Allah says: "And do not invalidate your deeds." As for interrupting it with a valid legal reason, it is permissible. So, one may interrupt it to kill a snake, or for fear of losing property, or to aid someone in distress. Rescuing innocent drowning people takes precedence over performing prayer. If it is possible to perform the permitted action without invalidating the prayer, then one should do so; otherwise, one should interrupt it and restart.