The Great Commentary of Cornelius à Lapide
Luke 12:50
But I have a baptism to be baptized with. The Arabic says, "I have a baptism, and I shall be baptized with it:" That is, By the decree of God and of My own will and determination I owe (debeo) to be baptized.
And how am I straitened till it be accomplished! "This fire of love and zeal of the Holy Spirit, cannot break forth unless the flint of My body be first struck upon the cross, or rather, until I am baptized in the font of My own blood." This is like some fountains into which if we plunged a torch, by the wonderful power of nature, and an antiperistasis, it is lighted. Such, according to Pliny, is the fountain of Dodona (bk. ii. chap. 103). Our brethren of Coimbra, in Meteora (tract. ix. chap. 7), say that there is another in Epirus, and a third in India, the waters of which burn; another, again, which formerly took its name from Jupiter Ammon. This just before the dawn is tepid, at midday it becomes cold, it is warm in the evening, and it boils at midnight. Similar springs are found near Naples, in France, and other places. Our Lord, then, compares His passion to these. This is like a boiling fountain which has aroused, and still arouses, the fire of love in the minds of the faithful. For equally by the merit of the cross and passion of Christ and by His example does this fire burst forth. He calls His death and passion a baptism, because He was clearly sunk and overwhelmed in it, as says the Psalm, "I sink in deep mire where there is no standing, I am come into deep waters, where the floods overflow me," Psalms 69:2.
And how am I straitened until it be accomplished? That is, "I am afflicted and tormented by the longing to die for the salvation of men and by My death to kindle this flame." Euthymius: "I am anxious because of its slowness;" and Theophylact: "How am I straitened," that is, how anxious and oppressed am I until it be performed, "for I thirst for death for the good of all men." So S. Ambrose, Bede, and others. The Arabic has, "I am narrowed for its performance." S. Irenæus 1. 18 reads, "I earnestly hasten to it." For the hearts of the anxious are wont to be contracted and as it were compressed by such, whilst those of the joyful are expanded and dilated. De Lyra, therefore, renders it amiss, "I am narrowed," he says, "that is, I am filled with dread, according to the words, 'My soul is sorrowful even unto death.'" This, indeed, was a feeling natural to the soul of Christ, but He quelled and overcame it when He said, "Not as I will, but as Thou wilt."
Morally. Observe how great was the zeal of Christ, how great His love, how deep His thirst for our salvation. For it was this that raised in Him so great a thirst for His Passion, death, and crucifixion, cruel as they were, so that His heart, between their infliction and the waiting for them, was compressed, as between the two stones of a mill, and brought into the greatest straits; or placed, as it were, in a vice and compressed with anguish, lest what He loved should be refused or delayed. Christ then was urged and, as it were, burnt up by the utmost longing to offer Himself up to God as a holocaust on the altar of the cross, that, as far as in Him lay, He might sanctify, save, and bless all men.
This zeal, His thirst, He impressed upon the Apostles and apostolic men, who thirsted for crosses, labours, pains, torments, and martyrdoms, for the glory of God: that they might propagate the gospel of Christ throughout the whole world and save as many as they could. This is the holiness of the Gospel, this is the perfection of virtue, this is the crown of the Apostleship. S. Andrew's salutations of the cross, and his earnest longing for it, are known. "Hail, precious cross, long desired, and at last ready for my longing soul! Secure and rejoicing I come to thee; do thou with joy accept me, and through Thyself do Thou receive me who by dying for me hast redeemed me." S. Laurence said to the Emperor Valerian, when he showed to him with threats, flames, wheels, scorpions, wild beasts: "For this table I hunger, I thirst. There is no famished man who desires food, there is no one perishing of thirst who craves for water, as greedily as I court and covet all these torments, that I may repay to Christ my Saviour, pain for pain, death for death." S. Vicentius to Dacian: "No one living has conferred on me greater gifts than thou, who torturest and crucifiest me, for with as many tortures as thou afflictest me with with so many crowns of martyrdom dost thou adorn me." And to the executioners, "How slow are ye, how slothful!"
S. Agatha to Quintianus, "Why are you so slow? What do you wait for? scourge, lacerate, burn, cut down, mangle, slay my body, for the more you crucify me, the more good you confer upon me, and the more favour and grace shall I receive from my spouse Jesus Christ." Such were the vows and such the words of SS. Agnes, Lucia, Dorothea, Cœcilia, and other Martyrs.