How can anyone enter a strong man’s house and steal his property, unless he first ties up the strong man? Then he can plunder his house (Matthew 12:29).
Then He [Jesus] told them, “No one can enter a strong man’s house without first tying him up. Then he can plunder the strong man’s house” (Mark 3:27).
Jesus refers to Satan as the “strong man” and to Himself as the One who enters the house and plunders the place. Of course, before Satan allows his domain to be “plundered,” he must be incapacitated. Jesus was not in league with Satan, as the scribes suggested, but had come to the earth, to what is essentially Satan’s “house” because he is the prince of this world (1 John 5:19), in order to bind Satan and plunder his “goods,” which are the souls of men (John 17:15; Luke 4:18; Ephesians 4:8).
The "goods" that He plundered were not only the souls of men redeemed from the eternal consequences of sins, but He also plundered the temporal consequences of our sins - concupiscence & suffering - by carrying them to the cross and redeeming them too. He didn't remove temptation and suffering in this life, he made them a source of merit and glory. We gain this glory as we struggle to overcome the temptations that we face and to offer the suffering and difficulties we encounter in this life, in, with and through Him to the glory of the Father for the salvation of souls.
A parallel passage says this: “When a strong man, fully armed, guards his own house, his possessions are safe. But when someone stronger attacks and overpowers him, he takes away the armor in which the man trusted and divides up his plunder” (Luke 11:21–22). Satan is strong, and he holds possessions that he guards jealously. But Jesus is the One who was and is stronger than the strong man. He is the only One who can bind the strong man and rescue us from his clutches (see John 12:31).
Original Source: https://www.gotquestions.org/bind-the-strongman.html