To Virtue add Knowledge

 2Pet 1:5 And beside this, giving all diligence, add to your faith virtue; and to virtue knowledge;

This word is first seen in the NT in the book of Luke. Both times linked to the way of salvation.

Luke 1:76 And thou, child, shalt be called the prophet of the Highest: for thou shalt go before the face of the Lord to prepare his ways; 77 To give knowledge of salvation unto his people by the remission of their sins,

Here Zacharias prophesies of the calling of his son John, known later as the Baptist. He was to give knowledge of salvation, manifested by the remission of sins. This is an incredible and Holy calling.

Next we see it used in in the opposite way by Jesus.

Luke 11:52 Woe unto you, lawyers! for ye have taken away the key of knowledge: ye entered not in yourselves, and them that were entering in ye hindered.

Jesus had pointed to John as the forerunner for his ministry and asked the Pharisees to tell him whether John was from God or not, they could not or would not tell. He also pointed to John as more than a prophet and one who was not shaken with the wind.

In Rom 2:20 the knowledge is likened to a form because the so called teachers have not put away sin.

In Rom 11:33 we see the knowledge of God as the higher ways...

In Rom 15:14 Paul declares that those in Rome to whom he was writing were full of this knowledge and able to admonish one another

He also in 1Cor  uses the word as knowledge of what is going on with meat and drink offered to idols and how to use this knowledge correctly. He also talks of "the word of Knowledge" as a gift of the Holy Spirit. These all describe a higher knowledge

It is found in Jesus:

2Cor 4:6 For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ.

The treasure of wisdom and knowledge is in Jesus (Col 2:3)

In 2Cor 6:6 we see knowledge listed as part of the equipment of the ministers of God

In 1Cor 13:8 we see that love is greater than knowledge and in Eph 3:19 we see that the love of Christ passes knowledge.

This knowledge of Jesus is excellent and Paul suffered loss of all in this life to obtain it (Phil 3:8)

Husbands are to dwell with their wives according to this knowledge (1Pet 3:7)

We can grow in it (2Pet 3:18)

The last point is look at 1Tim 6:20-21

20 O Timothy, keep that which is committed to thy trust, avoiding profane and vain babblings, and oppositions of science falsely so called: 21 Which some professing have erred concerning the faith. Grace be with thee. Amen.

The word translated science here is the same as all those translated knowledge. There is a knowledge which is contrary to the knowledge of God, it is falsely called knowledge, but will cause one to err concerning the faith.

So, we want to add to our virtue, the higher ways of God, the knowledge of God. It is knowledge of the true way of salvation and is only found in Jesus. It is equipment we need to walk as ministers of God and is associated with knowledge of sin and the putting away of it.