First Time Obedience.  It's been elevated to a bizarre status in the conservative Christian parenting world.  When "they" are not trying to stretch scripture to justify FTO, they use the "safety defense".

You know.  "We must train our children to obey because there might come a time when my words need to save their life".  It's a red herring.  Really, it's just an inaccurate and ridiculous justification for repeatedly hurting your kids.

You can't punish them enough to keep them safe.  If you have a child young enough where running out into the road, outlets, scissors, knives and stairs are a safety issue; the only reasonable prevention is supervision.  You can't repeatedly spank a 2 year old, set them in the driveway and walk away.  You can't make a small child responsible for their own safety. 

It doesn't even help to 'teach them how serious this is".  If they are of running age, they are also of an age where they will not understand the magnitude of danger involved.  They won't connect "danger" with the punishment.  If spanking works/ed with your child for safety, it's because your child had that kind of personality.  A runner will require supervision, regardless of how many times you have hurt them in the past.

I do not see the Biblical, pragmatic or practical justification for First Time Obedience.  That said, I do expect my children to age appropriately learn to obey my words.