He told her, “Go, call your HUSBAND and come back.” Why bothered?

[TonyChanYT]

Jesus spoke to the Samaritan woman at the well in John 4:

13 Jesus answered, “Everyone who drinks this water will be thirsty again, 14 but whoever drinks the water I give them will never thirst. Indeed, the water I give them will become in them a spring of water welling up to eternal life.”

Jesus was not talking about the physical water but the water of eternal life.

15 The woman said to him, “Sir, give me this water so that I won’t get thirsty and have to keep coming here to draw water.”

The woman didn't get the point and confused the two kinds of water. They were on different wavelengths. But instead of giving the woman a systematic theology to delineate the two concepts:

16 He told her, “Go, call your husband and come back.”

Call your husband and bring him here. He might be able to help you understand. No, not really. Jesus didn't appeal to her intellect but to her conscience.

17 “I have no husband,” she replied.

Right here, Jesus performed a miracle of supernatural knowledge.

Jesus said to her, “You are right when you say you have no husband. 18The fact is, you have had five husbands, and the man you now have is not your husband. What you have just said is quite true.”

She didn't need more husbands. Jesus opened her conscience so that she could see her need for eternal water. That's the one true husband that she would ever need.

19 “Sir,” the woman said, “I can see that you are a prophet.

Point taken. Now, she was receptive and not defensive.

What is the significance of Jesus asking her to call her Husband (John 4:16)?

Jesus pointed to her spiritual needs and opened her conscience to the living water, which was what she needed.

Jeremiah 17:

13 they have abandoned the LORD,
the fountain of living water.

The husband-request trick worked:

39 Many of the Samaritans from that town believed in him because of the woman’s testimony, “He told me everything I ever did.”