Adam Clarke on John 5:21

As the Father raised up the dead - This he did in the case of the widow's son at Sarepta, 1Kgs 17:22, by the ministry of the Prophet Elijah. And again, in the case of the Shunamite's son, 2Kgs 4:32-35, by the ministry of the Prophet Elisha.

The Son quickeneth whom he will - He raiseth from death to life whomsoever he pleases. So he did, for he raised the ruler's daughter, Mar 5:35-42; the widow's son at Nain, Luk 7:11-15; and Lazarus, at Bethany, John 11:14-44.

Whom he will. Here our Lord points out his sovereign power and independence; he gives life according to his own will - not being obliged to supplicate for the power by which it was done, as the prophets did; his own will being absolute and sufficient in every case.