"I will make you into a great nation and I will bless you; I will make your name great, and you will be a blessing." (Gen 12:2 NIV)
As a pastor and Sunday School teacher I have always taught that verse means God's Covenanted People (first the genetic offspring of Abraham, the Jews, then his spiritual offspring, the Church) were "blessed to be a blessing." I have taught that the passage could be correctly translated, "...I will bless you...so that (or in order that) you will be a blessing to others."
But I recently discovered that in both the Hebrew and the LXX, the phrase "you will be a blessing" in verse 2 is in the imperative. It is not a statement, it is a command. In other words, God is saying, "I'm going to make you a great nation and I will bless you; I will make your name great, and because I will do this for you, I command you to bless others." The Hebrew people forfeited their blessing in part because they refused to obey the command to be a blessing to other nations.
In the Bible, the words “nation” and “nations” refer more to people groups (ethnic, cultural, etc.) than to geographic boundaries. So I can’t help but wonder what God thinks of Tea Party type Christians who promote cultural isolation and building walls to keep the “nations” out rather than building bridges of blessings.
In my own personal struggle between balancing time spent in personal piety (prayer, Bible study, etc.) and service to others (chaplaincy, S.S. teaching, advocating for "the least of these" (Matt 25:40), visiting/helping those who are hurting in some way, etc.), it does seem to indicate that being a blessing is at least as important as being blessed.