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You'll find few Protestants will address themselves as "the elect" anymore. It's not fashionable. Those who truly understand the term "elect" find within it a sense of humility since it means that for no understandable reason God had mercy on us.
I do not understand what you mean by it being a commandment.
Well, the Orthodox would simply say "because He loves us more than we could ever love Him."
But, more importantly, how do we know He has mercy on us? When we pray, we simply ask for mercy. We don't know, but we hope and believe in His love. "Now faith is the substance of things hoped for, the evidence of things not seen" (Heb 11:1)
I do not understand what you mean by it being a commandment
God chose Moses to do a formidable task. Christ chose the Apostles. There were many chosen God's people who accomplished specific tasks as God's elect. The Jews were chosen to spread the knowledge of God, so that "salvation is from the Jews." (Jn 4:22) And, as Christians, we are to serve as the light of God for the world to see and glorify Him. (cf Mat 5:16)