Proverbs 17:18
16 What’s the point of a fool having money in hand to buy wisdom when his head is empty? 17 A friend loves at all times, and a relative is born to help in adversity. 18 The one who lacks sense strikes hands in pledge and puts up financial security for his neighbor. 19 The one who loves a quarrel loves transgression; whoever builds his gate high seeks destruction. 20 The one who has a perverse heart does not find good, and the one who is deceitful in speech falls into trouble.
Sirach 29:20
Ben Sira, Ecclesiasticus18 Being surety has ruined many who were prosperous, and has tossed them about like waves of the sea; it has driven the influential into exile, and they have wandered among foreign nations. 19 The sinner comes to grief through surety; his pursuit of gain involves him in lawsuits. 20 Assist your neighbor to the best of your ability, but be careful not to fall yourself. 21 The necessities of life are water, bread, and clothing, and also a house to assure privacy. 22 Better is the life of the poor under their own crude roof than sumptuous food in the house of others.
Notes and References
"... In the overall context of Sirach 8, verses 12-13 are pessimistically cautious, brief and pragmatic.11 The concern of these statements is to protect the students from being exploited and they thus share the reservations of Ps 37:21 regarding loans to the unscrupulous and are also in basic continuity with the warnings against surety in Proverbs, which are consistently negative in nature (compare Proverbs 6:1-5; 11:15; 17:18; 22:26-27). As we will see in the next section, the discussion of loans and surety in chapter 8 lacks the more explicitly theological grounding found in the later discussion of chapter 29 concerning the connection to the commands of the Torah or the general benevolence of these acts, especially notable since this larger section follows the admonitions to give generously to those in need (7:32-36). Commentators are agreed that 29:1 begins a new pericope because of the obvious change in content, from the issue of controlling one’s tongue to financial matters. Within chapter 29 itself, commentators divide the text differently. All commentators see a break between verses 20 and 21 and thus classify 29:21-28 as a subunit. Gilbert notes that the presence of (“take care”) in 28:26 and 29:20 brackets 29:1-20 as a distinct section. Beginning in 29:21 the discussion shifts from the perspective of those with means who are exhorted to give generously (verses 1-20) to the virtue of moderation in contrast to the impoverished ruin that results from greedy financial mismanagement ..."
Gregory, Bradley C. Like an Everlasting Signet Ring: Generosity in the Book of Sirach (p. 133) De Gruyter, 2010