Whom the Lord and this people - choose - Here is an equivocation; Hushai meant in his heart that God and all the people of Israel had chosen David; but he spake so as to make Absalom believe that he spoke of him: for whatever of insincerity may appear in this, Hushai is alone answerable. What he says afterwards may be understood in the same way.

should I not serve

2 Samuel 15:34 But if you return to the city, and say to Absalom, I will be your servant, O king; as I have been your father's servant till now...

1 Samuel 28:2 And David said to Achish, Surely you shall know what your servant can do. And Achish said to David...

1 Samuel 29:8 And David said to Achish, But what have I done? and what have you found in your servant so long as I have been with you to this day...

Psalm 55:21 The words of his mouth were smoother than butter, but war was in his heart: his words were softer than oil, yet were they drawn swords.

Galatians 2:13 And the other Jews dissembled likewise with him; so that Barnabas also was carried away with their dissimulation.

The Godly are in Some Sense Already Blessed
I proceed now to the second aphorism or conclusion, that the godly are in some sense already blessed. The saints are blessed not only when they are apprehended by God, but while they are travellers to glory. They are blessed before they are crowned. This seems a paradox to flesh and blood. What, reproached and maligned, yet blessed! A man that looks upon the children of God with a carnal eye and sees how they are afflicted, and like the ship in the gospel which was covered with waves' (Matthew 8:24), …
Thomas Watson—The Beatitudes: An Exposition of Matthew 5:1-12