Walking in the fear of the Lord: Acts 9:31.
“Then had the churches rest throughout all Judaea and Galilee and Samaria, and were edified; and walking in the fear of the Lord, and in the comfort of the Holy Ghost, were multiplied." (Ac 9:31)
“Therefore, my beloved, as you have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling;" (Phil:2:12). The first verse talks about the effect that Paul’s conversion had on the disciples. In the second verse, Paul is warning the Philippians to think about their own salvation with fear and trembling.

The idea of "fear and trembling" in connection with God is not a popular idea today. People prefer to hear about God's love, longsuffering and mercy rather than the fire and brimstone sermons of a few years back. We do not like to think about God’s righteous anger, we say that our God is not like that. This is probably why we are so indifferent to our sins and mistakes, we seem to have taken God for granted. We tend to believe that God will always forgive our sins, small or big.
The word fear means terror, dread, something which strikes terror. The fear of the Lord is defined as ‘reverence‘ or ‘awe’ combined with  ‘trembling’. Just as one trembles in the presence of one who could take our life, so also Jesus (Yahshua) taught us to fear the Lord. So the fear of the Lord will mean reverence, awe, being afraid to offend God(Yahweh) in anyway. Fear of God(Yahweh) means a trembling and quaking if one knows they have offended God(Yahweh) and have not obtained forgiveness (Heb.10:26-27; 31-31; 12: 28-29)

From the book of Proverbs, we learn that
1. The "fear of the Lord" is the beginning of knowledge - Pr 1:7
2. The "fear of the Lord" will cause one to hate evil - Pr 8:13
3. The "fear of the Lord" will prolong life - Pr 10:27
4. The "fear of the Lord" provides strong confidence and is a fountain of life - Pr 14:26-27
5. The "fear of the Lord" prompts one to depart from evil – Pr.16:6
6. The "fear of the Lord" leads to a satisfying life, and spares one from much evil - Pr 19:23
7. The "fear of the Lord" is the way to riches, honor, and life! Pr 22:4

Without the fear of the Lord we shut ourselves from the doors of the treasures of God's wisdom and knowledge. We will play with evil and be corrupted by it. Our lives are likely to be shortened by our refusal to heed God's word. We will not come to know the love of God that gives us assurance and confidence of our salvation. When we fall into sin, we will not be motivated to repent and turn to God!   We will not be motivated to truly "work out our own salvation"!

Without the fear of the Lord, we cannot please God(Yahweh)  Only the person who trembles at God(Yahweh)’s Word has His promise to receive His tender mercy! (Ps 103:17-18).

The fear of the Lord comes through the word of God(Yahweh).
Just as "faith comes by hearing, and hearing by the word of God(Yahweh) " (Ro 10:17), the same can be said for the "fear of the Lord"!
In Deut 31:10-13 we read that the children of Israel were told to gather every seven years to read and hear the Word so that they may learn to fear the Lord. When you start to fear the Lord, your heart will not be hardened. God(Yahweh) will render to everyman according to his deeds (Rom.2:6). Read Peter’s warning in 2 Pet.3:7.
The word of God, properly used, will maintain a proper balance in our relationship with God(Yahweh).
It is important to emphasize that we must read ALL of God (Yahweh)’s Word. Some read only those portions which reveal God's love and mercy, and have no "fear of the Lord". They develop an attitude of permissiveness and taking Him for granted. Others emphasize the "fire, hell and brimstone" passages, and know nothing of God's everlasting loving kindness and develop a feeling of terror of God(Yahweh) forgetting His grace and compassion.

The Psalmist said, "God is greatly to be feared in the assembly of the saints, and to be had in reverence of all them that are about him." (Psalms 89:7)

The warning to fear God(Yahweh) is necessary, because it is written in Hebrews:  "Let us therefore fear, lest, a promise being left [us] of entering into his rest, any of you should seem to come short of it.  For unto us was the gospel preached, as well as unto them: but the word preached did not profit them, not being mixed with faith in them that heard it." (Hebrews 4:1-2)

 "Let us labour therefore to enter into that rest, lest any man fall after the same example of unbelief." (Hebrews 4:11). With the proper "fear of the Lord", we will "work out our salvation", we will "labour to enter into that heavenly rest"!

"Having therefore these promises, dearly beloved, let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God." (2Cor. 7:1)
If we desire to be truly wise, then let us begin by developing the fear of the Lord. “For His knowledge has given us great and precious promises”. 2 Pet. 1:2-4.