John Calvin Commentary Psalms 18:50

"Great deliverance giveth he to his king, And showeth lovingkindness to his anointed, To David and to his seed, for evermore." — Psalms 18:50 (ASV)

He works great deliverances, etc. This concluding verse clearly shows why God had exercised such goodness and liberality towards David, namely, because he had anointed him to be king. By calling himself God’s king, David testifies that he had not rashly rushed into that office, nor was thrust into it by conspiracies and wicked intrigues, but, on the contrary, reigned by lawful right, since it was the will of God that he should be king.

This he proves by the ceremony of anointing; for God, in anointing him by the hand of Samuel, had asserted his right to reign not less than if he had visibly stretched out his hand from heaven to place and establish him on the royal throne. This election, he says, was confirmed by a continued series of great deliverances; and from this it follows, that all who enter on any course without having the call of God can be accused of openly making war against him.

At the same time, he attributes these deliverances to the goodness of God as their cause, to teach us that this kingdom was founded purely and simply upon the good pleasure of God. Furthermore, from the concluding sentence of the psalm, it appears, as I have said before, that David does not here so much recount historically the unique and varied instances of the grace of God which he had personally experienced, as predict the everlasting duration of his kingdom.

And it is to be observed that by the word seed we are not to understand all his descendants indiscriminately; but we are to consider it as particularly referring to that successor of David of whom God had spoken in 2 Samuel 7:12, promising that he would be a father to him. As it had been predicted that his kingdom would continue as long as the sun and the moon should shine in the heavens, the prophecy must necessarily be viewed as descending to him who was to be king not for a time, but forever. David, therefore, commends his seed to us, as honored by that remarkable promise, which fully applies neither to Solomon nor to any other of his successors, but to the only begotten Son of God; as the apostle, in his Epistle to the Hebrews (Hebrews 1:4), teaches us that this is a dignity in which he excels the angels. In conclusion, we will then only properly profit in the study of this psalm when we are led by the contemplation of the shadow and type to him who is the substance.