The following is an excerpt from
The MacArthur New Testament Commentary on John 1.
And He said to him, “Truly, truly, I say to you, you will see the heavens opened and the angels of God ascending and descending on the Son of Man.” (1:51)
Speaking specifically of those greater things that Nathanael and the other disciples would see, Jesus solemnly assured him, “Truly, truly, I say to you, you will see the heavens opened and the angels of God ascending and descending on the Son of Man.” Jesus was probably alluding to Jacob’s dream, in which he saw angels ascending and descending from heaven on a ladder (Gen. 28:12). The point of this statement is that Jesus is the link between heaven and earth, the revealer of heavenly truth to men (1:17; 14:6; Eph. 4:21), the “one mediator … between God and men” (1 Tim. 2:5), and the mediator of a new (Heb. 9:14; 12:24) and better (Heb. 8:6) covenant. In John 3:13 He declared to Nicodemus, “No one has ascended into heaven, but He who descended from heaven: the Son of Man” (cf. 6:33, 38, 41–42, 50–51, 58, 62; 13:3; 16:28; 17:8). That truth would become increasingly clear to Nathanael and the rest of the disciples as they observed Jesus’ life and ministry.
This is the first of thirteen occurrences in John’s gospel of the title Son of Man, Jesus’ favorite way of referring to Himself (He did so about eighty times in the gospels). In John’s gospel, it is associated with Jesus’ suffering and death (3:14; 8:28; 12:34), His provision of salvation (6:27, 53), and His authority to judge (5:27; 9:35, 39). In the future, the Son of Man will receive the kingdom from the Ancient of Days (Dan. 7:13–14). As with His other titles in this section, Nathanael (and the others who were present) did not immediately grasp the full significance of what it meant for Jesus to be the Son of Man.
This passage, which records Jesus’ call of His first disciples to salvation, pictures the balance of salvation taught throughout Scripture. Salvation takes place when seeking souls come in faith to the Savior who has already sought them.