^3:8 I know what you have done. See, I have opened a door in front of you that no one can shut. You only have a little strength, but you have paid attention to my word and have not denied my name.

I know what you have done.

There is no indication what those deeds were. They must have been OK if the Philadelphians are complemented later in this verse for not denying His NAME.

SEE,

1. I have opened a door in front of you that no one can shut.

   Jesus says that He opened the door (and He has the keys) (John 10:1-18). This may reflect the fact that Philadelphia was on the crossing of two major highways and was strategically located to spread the Word of God throughout Asia.
   Our access to God is through the OPEN DOOR (Romans 5:1-2).
   We are filled with the fruit of righteousness (Philippians 1:9-11) which, in turn, becomes our strength (Philippians 4:13).

You

• only have a little strength, but

When there is little POWER, then the believer must TRUST God to provide a way (in His time). Paul recognized God's OPEN DOOR and timing in Ephesus (1 Corinthians 16:8-9). Paul always looked for the OPEN DOOR. (Colossians 4:2-4).

• you have paid attention to my word and

  The pressures of daily living are great to dilute, compromise, (or worst) ignore the WORD of God. The Philadelphians KEPT the word .... how can you KEEP what you don't know or even take the time to read THE BIBLE (GOD'S WORD)! Don't be moved away from the hope of the Gospel (Colossians 1:21-23).

• have not denied my name.

Jude 3-4 explains that certain persons will creep in unawares who turn the grace of God into licentiousness. You can always tell who these persons are because they deny the Lord Jesus Christ. Jesus, himself, says we are to deny ourselves NOT Him (Matthew 16:24-25).