Charles H. Spurgeon on Psalms 40:7

Then said I, Lo, I come, to wit, as surety, to pay the ransom, and to do thy will, O God. Every word carrieth a special emphasis as 1. The time, then, even so soon as he perceived that his Father had prepared his body for such an end, then, without delay. This speed implies forwardness and readiness; he would lose no opportunity. 2. His profession in this word, said I; he did not closely, secretly, timorously, as being ashamed thereof, but he maketh profession beforehand. 3. This note of observation, Lo, this is a kind of calling angels and men to witness, and a desire that all might know his inward intention, and the disposition of his heart; wherein was as great a willingness as any could have to anything. 4. An offering of himself without any enforcement or compulsion; this he manifests in this word, I come. 5. That very instant set out in the present tense, I come; he puts it not off to a future and uncertain time, but even in that moment, he saith, I come. 6. The first person twice expressed, thus, "I said, ""I come." He sends not another person, nor substitutes any in his room; but he, even he himself in his own person, comes. All which do abundantly evidence Christ's singular readiness and willingness, as our surety, to do his Father's will, though it were by suffering, and by being made a sacrifice for our sins. Thomas Brooks.