Oil into the lamps

Mt 25 talks about the 10 virgins.
The wise ones took oil as well in jars.

That means to me, the time for buying oil is different from using it. We need to pray and fast and read Bible, just for filling up our lamps, so that the Spirit would be able to light the fire in us in the moment He wants - when it is needed.

So there is no useless prayer or Bible reading. Mostly it is just filling the oil, but it is necessary. Then the fire comes and we can see something in this light of Spirit.
This is what "LABOUR in prayer" means for me.