The disciples requested of Jesus, “Lord, teach us to pray, as John taught his disciples.” (Luke 11:1). To some this seems like a strange question because, to be sure, a child can breathe out a good prayer. Herein lies the apparent 
conundrum: We are to have faith like that of a child (e.g. Mt. 18:3), yet we are to be mature in our Christian understanding (e.g. Eph. 4:14).
There is, however, no conundrum. We are to approach our heavenly Father even as dear children approach their dear earthly fathers—with a trusting, loving heart. We can only have such a heart because Christ has reconciled us to the Father by His death and resurrection, baptizing us into this wondrous reality, bringing us into God’s family. But even as my three year old son asked his father for a motorized mini-scooter, so too some are prone to approach the heavenly Father with requests that are not in line with His will. The better we understand the faith, the more our prayers will be in line with His will. Thus when the Apostles requested that Jesus teach them to pray, it was in effect a request that Jesus teach them what they should ask for—certainly with the faith of a child.
So the Lord Jesus taught the ultimate prayer, teaching us to request of the Father that which we should understand to be appropriate for prayer. We should also note that the “prayerbook” for God’s people is the Psalms, which, if one studies them, are an amplification of what Jesus condenses in the Lord’s Prayer. Note also that the Lord’s Prayer is entirely a petitioning prayer, but the Psalms also teach us how to offer prayers of praise, thanksgiving and confession of faith.
The one petition of the Lord’s Prayer most commonly—almost naturally—prayed is: “Give us this day our daily bread.” In The Small Catechism we are appropriately taught that this is the petition that covers our everyday bodily needs. Thus when people ask for healing, for good weather, for peace, for a job, for abundant and good food, this is the petition that covers these, and even more. Unfortunately many of us become “daily bread” pray-ers, often practically ignoring the other petitions of the Lord’s Prayer.
However Jesus, as He concludes this section of teaching on prayer, actually gives us the one request that summarizes all of the other petitions of the Lord’s Prayer. When we ask and seek and knock before the Father’s door, requesting His name be hallowed, His kingdom come, His will be done, that He forgive and we forgive, that we not be led into temptation, and that He deliver us from evil, …what are we asking for? Jesus summarizes: “If you then, who are evil, know how to give good gifts to your children, how much more will the heavenly Father give the Holy Spirit to those who ask him!” (v. 13).
After our Lord’s death and resurrection the one gift needed by His church, needed by individual Christians, is the gift of the Holy Spirit. This request was uniquely answered on Pentecost, but the prayer and the giving of the Holy Spirit continue to be the heart and request of the petitions of the Lord’s Prayer. (See The Small Catechism🙂 Pointing to Christ: by the Spirit God’s Word is taught in its truth and we lead holy lives; by the Spirit the kingdom comes; by the Spirit God‘s will is done as anti-Christian wills are quashed by the Spirit; by the Spirit forgiveness is breathed out from Christ; by the Spirit we are led away from misbelief, despair and other shame and vice; by the Spirit we look to Christ and are delivered from every evil, ultimately, in Christ, having our bodies raised on the Last Day by the Holy Spirit. Thus we pray with the faith of a child but with the understanding given by Christ.