Leah named her fourth son Judah, saying what?

Answer: "This time I will praise the LORD"

At Judah's birth Leah said, "This time I will praise the LORD" (KJV: "Now will I praise the LORD"). Then she stopped bearing.

“And once more she conceived and gave birth to a son and said, “This time I will praise the LORD.” So she named him Judah. Then Leah stopped having children.”— Genesis 29:35 (BSB)