Again, the next day, John stood with two of his disciples. And looking at Jesus as He walked, he said, “Behold the Lamb of God!” – John 1:35,36

I think that John meant (for) his disciples to consider when he said to them, “Behold the Lamb of God!” So, we say to you, “Think of Him, study Him, know all that you (can) about Him, look Him up and down. He is God; do you understand that He stood (in) the sinner’ stead? He is man; do you know how near akin He is to you, how sympathetic He is, a brother born for your adversity?” The person of Christ is a great marvel; how God and man can be in one person, it is impossible for us to tell. We believe what we cannot comprehend; and we rejoice in what we cannot understand. He whom God has provided to be your Saviour is both God and man; He can lay His hand upon both parties, He can touch your manhood in its weakness, and touch the Godhead in its all-sufficiency. Study Christ; the most excellent of all the sciences in the knowledge of a crucified Saviour. He is most learned in the university of heaven who knows most of Christ. He who hath known most of Him still says that His love surpasseth knowledge. Behold Him, then, with wonder, and behold Him with thankfulness.

But when John says, “Behold the Lamb of God!” he means more that wondering or considering. “Looking” is used in Scripture for faith: “Look unto Me, and be ye saved.” Therefore we sing-

There is life for a look at the crucified One,
There is life at this moment for thee!

Beholding is a steady kind of looking. Believe then, in Christ with a solid, abiding confidence. Come, ye sinners, come, and trust your Saviour…Believe that He is able and willing to save you, and trust Him to do so.

Venture on Him, venture wholly,
Let no other trust intrude.

~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2329.cfm