This is a Psalm of Asaph. Asaph means “gathering”, and both he and Korah were both prophets who were asked to prophesy about what Jesus would do. Generally, his collection of Psalms start from about chapter 73 (depending on which manuscript you are relying on), but here Psalm 50 is the first independent Psalm related to him.
In particular, the person Asaph is referred to in 1 Chronicles 25, which describes the sons of Asaph, and of Heman, and of Jeduthun, who “prophesied with lyres, with harps, and with cymbals” – Jeduthun, “who prophesied with the lyre in thanksgiving and praise to the LORD” (1 Chronicles 25:3) – thus Asaph, Heman and Jeduthun were the three under the direct order of the king (v.6). As an interesting side note – in Nehemiah 11, it is the offspring of Asaph and Jeduthun who survive the exile and return, as described in v.17 of that chapter (and Heman is not mentioned), and of the Psalms written by David, it is only to Asaph and Jeduthun that the Psalms are dedicated to.
There is also a common theme of prophesied judgment in Asaph’s psalms, which we will look at in greater detail from Book 3 of the Psalms onwards (i.e. chapters 73 to 89).
In chapter 50, we see there is a common theme of God speaking with dynamic brilliance – He shines forth (v.2), He comes, devouring fire, around him a mighty tempest (v.3); He calls to the heavens above and to the earth (v.4); the heavens declare his righteousness (v.6); He does not keep silent (vv.3, 21). That is directly contrasted with our response – that we give him burnt offerings (v.8) which are in fact all his already (vv.9-13). True thanksgiving, we are taught, is to simply call to Him to deliver us (vv.14-15), such that we glorify him because of his works, not ours! (v.23) That is the revelation of His judgment. He will not remain silent, but in the day that He comes to us – which may very well be this day – we must be sensitive and be kept accountable. Consider the judgment on the wicked man: the Lord describes him as one who hates discipline (v.17); casts His words behind him (v.17); associates himself with thieves and adulterers (v.18); fails to rein in his/her mouth and instead allow it to freely speak evil and frame deceit, slandering your own brother (vv.19-20). The only One who need not rein in his mouth is God, who speaks creation into being (c.f. Genesis 1); whereas, what comes out of the mouth proceeds from the heart (Matthew 15), and our heart is ever so filled with sin!
He is forever faithful. He does not forget, even though we do so everyday. And He will not remain silent. Let us therefore praise Him not merely with our lips, but with the heart of thankgiving.