Suppose...you are a mother or father with a son who is straying from the path of righteousness...You can do much to pray him home...to fast him home. You can repent enough of your own sins that, through your sacrifice, the Lord may intervene more in his life and save the boy. It's not that you're paying for your own sins--Jesus did that. But through your agency, through your sacrifice, you are able to receive blessings that you otherwise would not be able to obtain. (Of course, these things still depend on the agency of others--our prayers can't supersede the agency of those we're praying for. But sacrifice and fervent prayer can do much to help. With such prayer we can accomplish much--even if it doesn't bring our loved ones all the way home.)~Gene R. Cook
And again, the angel said: Behold, the Lord hath heard...the prayers of his servant, Alma, who is thy father; for he has prayed with much faith concerning thee that thou mightest be brought to the knowledge of the truth; therefore, for this prupose have I come to convince thee of the power and authority of God, that the prayers of his servants might be answered according to their faith.