A parable - See the notes at Matthew 13:3.
To this end - To show this.
Always - At all times. That is, we must not neglect regular stated seasons of prayer; we must seize on occasions of remarkable providences as afflictions or signal blessings to seek God in prayer; we must “always” maintain a spirit of prayer, or be in a proper frame to lift up our hearts to God for his blessing, and we must not grow weary though our prayer seems not to be answered.
Not to faint - Not to grow weary or give over. The parable is designed to teach us that, though our prayers should long appear to be unanswered, we should persevere, and not grow weary in supplication to God.