Ch. 1 – Although the letter is encouraging the whole church at Philippi, it also encourages, individual, new believers to be active for Christ from the first day of their conversion. It dispenses with the idea of “saved then sit” until one is “ready,” but rather encourages “saved and start” your work and walk of faith for Jesus.
Ch. 3 – Young or new believers do well to watch and even imitate mature, wise believers – those whose lives are a reflection, or image, of Jesus. Paul again warns, as he has in other letters, to avoid false, errant “brothers” who are known by their works and/or love of the flesh (or worldly ways).