Matthew 21:22 - Prayer Power

And all things, whatsoever ye shall ask in prayer, believing, ye
shall receive. Mat 21:22 (KJV)

This verse is not a guarantee that we can get 'anything' we want
simply by asking Jesus and believing. God does not grant requests that
would hurt us or others or that would violate his own nature or will.
Jesus' statement is not a blank check. To be fulfilled, our requests
must be in harmony with the principles of God's kingdom. The stronger
our belief, the more likely our prayers will be in line with God's
will, and then God will be happy to grant them. [Life Application SB]

Prayer is heaven's ordained means of success in the conflict
with sin and the development of Christian character. The divine
influences that come in answer to the prayer of faith will accomplish in
the soul of the suppliant all for which he pleads. For the pardon of
sin, for the Holy Spirit, for a Christlike temper, for wisdom and
strength to do His work, for any gift He has promised, we may ask; and
the promise is, "Ye shall receive."   AA564

Removing mountains, and rooting up of mountains, are phrases
very generally used to signify the removing or conquering great
difficulties-- getting through perplexities. So, many of the rabbis are termed
rooters up of mountains, because they were dexterous in removing
difficulties, solving cases of conscience, etc. In this sense our Lord's words
are to be understood. He that has faith will get through every
difficulty and perplexity; mountains shall become molehills or plains
before him. (Adam Clarke Commentary)

Faith is the soul, prayer is the body; both together make a
complete man for any service. Faith, if it be right, will excite prayer;
and prayer is not right, if it do not spring from faith. This is the
condition of our receiving-- we must ask in prayer, believing. (Matthew
Henry's Commentary)

"Faith" and "believing" in the NT are expressions that indicate
a sincere trust in God, and a genuine relationship with Him.
Christ's relationship with the Father made the miracle of answered prayer
not only a possibility, but a certainty. And when our prayers grow
out of a genuine relationship with the Lord, our prayers too can be
expressions not of uncertain hope, but of real confidence that we "will
receive." . [Victor Bible Background Commentary]

Where we get wrong in prayer is that we are so self-willed.  We
set ourselves to pray for things; we vow to sit up all night to
bring God round to our way of thinking; we use strong cryings, tears,
and protestations...  And then we are surprised if the fig-tree does
not wither, or the mountain remove.
Where are we wrong?...  There is too much of self and the energy
of the flesh in all this.  We can only believe for a thing when we
are in such union with God that his thought and purpose can freely
flow into us, suggesting what we should pray for, and leading us to
that point in which there is a perfect sympathy and understanding
between us and the divine mind....  Then the Spirit will lead you to ask
what is in the will of God to give, and you will know instantly that
the Spirit intercedes within you according to the will of God.  [F.
B. Meyer; Our Daily Homily; Spirit Filled Life Daily Devotional
Bible]