Albert Barnes Commentary Ruth 4:6

"And the near kinsman said, I cannot redeem it for myself, lest I mar mine own inheritance: take thou my right of redemption on thee; for I cannot redeem it." — Ruth 4:6 (ASV)

I mar mine own inheritance - The meaning of these words is doubtful. Some explain them by saying that the גאל gā'al already had a wife and children, and would not introduce strife into his family. Others think that there was a risk (which he would not incur) of the go’el’s own name being blotted out from his inheritance (Ruth 4:10). Others take the word translated as “mar” in the sense of wasting or spending. If he had to find the purchase-money, and support Naomi and Ruth, his own fortune would be broken down, if, as is likely, he was a man of slender means. Boaz, being a mighty man of wealth, could afford this.

Redeem thou my right ... - Literally, redeem my redemption—perform that act of redemption which properly belongs to me, but which I cannot perform.