Psalm 21 – Skeptic's Annotated Bible answered

1 The king shall joy in thy strength, O LORD; and in thy salvation how greatly shall he rejoice!

2 Thou hast given him his heart’s desire, and hast not withholden the request of his lips. Selah.

3 For thou preventest him with the blessings of goodness: thou settest a crown of pure gold on his head.

4 He asked life of thee, and thou gavest it him, even length of days for ever and ever.

5 His glory is great in thy salvation: honour and majesty hast thou laid upon him.

6 For thou hast made him most blessed for ever: thou hast made him exceeding glad with thy countenance.

7 For the king trusteth in the LORD, and through the mercy of the most High he shall not be moved.

8 Thine hand shall find out all thine enemies: thy right hand shall find out those that hate thee.

9 Thou shalt make them as a fiery oven in the time of thine anger: the LORD shall swallow them up in his wrath, and the fire shall devour them.

(21:9-10) If you make God angry, he'll burn you and your children to death.
What the Bible says about burning people to death

10 Their fruit shalt thou destroy from the earth, and their seed from among the children of men.

11 For they intended evil against thee: they imagined a mischievous device, which they are not able to perform.

12 Therefore shalt thou make them turn their back, when thou shalt make ready thine arrows upon thy strings against the face of them.

God will shoot his adversaries in the back with his arrows.

13 Be thou exalted, LORD, in thine own strength: so will we sing and praise thy power.