3Ne Ch13

The Lord continues to teach the Nephites with a prayer and told to lay up treasures in heaven. He also tells the twelve that were called to take no thought for temporal things because they will be provided for.
One key concept that the Lord tells the people is to do alms unto the poor while seeking no reward or else you are a hypocrite and will not get your reward in heaven (v1-4). The same concept goes with praying, it is a private, special practice that is not meant for the street corners but the closet, and the prayers should not be repetitive but sincere and heartfelt (v5-8). The Lord gives an example of how to offer a heartfelt prayers with respect and gratitude  in v9-13, and in that example he asks Father to forgive our debts as we forgive our debtors because we are required to forgive if we expect to be forgiven (v14-15).
Fasting should also be done only for the purpose and knowledge of yourself and God, for he will know you fast for the right reasons (v16-18). By doing these things in secret, you lay your treasures in heaven instead of earth because your desire is for heavenly reward and not earthly reward (v19-21). This concept is likened unto looking with your eye to light and it filling your whole body with light, and they same with dark, but you cannot look into both, or in other words, you cannot serve God and Mammon (v22-24).
Speaking to the Twelve, Christ says to remember what He has taught so they can teach it to the people, and worry not what to eat or drink because it's not as important as preaching and also because God will take care of all that, just like He causes the fowls to eat and lilies to grow without toiling, He will provide for you (v25-28). The great Solomon was not taken care of by God but you will be because of your faith and devotion to the Father in preaching to His children, the Nephites (v29-32). Seek first the kingdom of God and all things will be given unto you that you need in the present so there is no need to worry about tomorrow (v33-34).