'One' in the Bible

the one do it of love, knowing that I am set for the defence of the gospel;

Only let your manner of life be worthy of the gospel of Christ: that, whether I come and see you and be absent, I may hear of your state, that ye stand fast in one spirit, with one soul striving for the faith of the gospel;

make full my joy, that ye be of the same mind, having the same love, being of one accord, of one mind;

Brethren, I could not myself yet to have laid hold: but one thing I do , forgetting the things which are behind, and stretching forward to the things which are before,