"Who art thou, O great mountain? before Zerubbabel thou shalt become a plain: and he shall bring forth the headstone thereof with shoutings, crying, Grace, grace unto it." (Zechariah 4: 7)
When we read about mountains, the first idea to come to mind is nothing more than the Old Covenant, in which the Mosaic Law presented God's absolute standard, and revealed or revulsion, inability to keep the law, that sin would be transgression, and show our need for the Savior: Jesus!
The first mention of mountain occurs:
"And the waters prevailed exceedingly upon the earth; and all the high hills, that were under the whole heaven, were covered" (Genesis 7: 19)
Water speaks of the Holy Spirit, the Spirit of grace, and these waters speak of baptism as well, taking us from death in our trespasses to alive in Christ:
"37In the last day, that great day of the feast, Jesus stood and cried, saying, If any man thirst, let him come unto me, and drink. 38He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water. 39(But this spake he of the Spirit, which they that believe on him should receive: for the Holy Ghost was not yet given; because that Jesus was not yet glorified.)" (John 7: 37-39)
"21The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ: 22Who is gone into heaven, and is on the right hand of God; angels and authorities and powers being made subject unto him." (1 Peter 3: 21-22)
As written above, the Mountain speaks of the Old Covenant:
"For ye are not come unto the mount that might be touched, and that burned with fire, nor unto blackness, and darkness, and tempest, 19And the sound of a trumpet, and the voice of words; which voice they that heard intreated that the word should not be spoken to them any more: 20(For they could not endure that which was commanded, And if so much as a beast touch the mountain, it shall be stoned, or thrust through with a dart: 21And so terrible was the sight, that Moses said, I exceedingly fear and quake:)" (Hebrews 12: 18-21)
Furthermore, because we receive grace through faith (Ephesians 2: 8-9), we can understand what Jesus meant by this declaration:
"Jesus answered and said unto them, Verily I say unto you, If ye have faith, and doubt not, ye shall not only do this which is done to the fig tree, but also if ye shall say unto this mountain, Be thou removed, and be thou cast into the sea; it shall be done." (Mathew 21: 21)
We are called to grow in grace and knowledge of the Lord Jesus (2 Peter 3: 18) We speak forth the grace of God, and we will witness the mountains in our lives removed and cast into the sea!