When a person without a long history of paying his or her bills on time wants to obtain a loan to purchase a home or car, lenders are often reluctant to take the financial risk. Without a track record, that person’s promise to repay what he borrows is insufficient for the bank. The would-be borrower usually resorts to finding someone who does have a history of making good on their debts, asking them to put their name on the loan too. The co-signer’s promise assures the lender the loan will be repaid.
When someone makes a promise to us—whether for financial, marital, or other reasons—we expect them to keep it. We want to know that God will keep His promises too. When He promised Abraham that He would bless him and give him “many descendants” (Hebrews 6:14; see Genesis 22:17), Abraham took God at His word. As the Creator of all that exists, there is no one greater than He; only God could guarantee His own promise.
Abraham had to wait for the birth of his son (and never saw how innumerable his offspring would grow to be) (v. 15), but God proved faithful to His promise. When He promises to be with us always (Hebrews 13:5), to hold us securely (John 10:29), and to comfort us (2 Corinthians 1:3–4), we, too, can trust Him to be true to His word.