Jeremiah 35:19
Therefore thus saith the LORD of hosts, the God of Israel; Jonadab the son of Rechab shall not want a man to stand before me for ever. Therefore thus saith the LORD of hosts, the God of Israel; Jonadab the son of Rechab shall not want a man to stand before me for ever.
The promise is that Jonadab the son of Rechab shall not want a man to stand before God forever, meaning his descendants will always have a continuing and enduring place of service before Him. That lasting blessing was given because the Rechabites obeyed the commands of Jonadab their father, keeping all his precepts and doing all that he commanded them. Their constancy was fully proved in loyalty to their father's command not to drink wine, and nothing was required of them beyond what they were able to perform.
The blessing teaches that faithfulness and obedience to God's rightful requirements bring blessing. Their obedience stands in contrast to Judah and Jerusalem, who refused to hearken to God and heed His words and warnings. The contrast exposes aggravated disobedience and an unrighteous course, because God spoke rising early and sent all His servants the prophets calling His people to return from evil and amend their doings. The contrast shows that people who have received great light and warnings dishonor God when they turn from them to follow their own impulses. Their obedience shows how much more reverence is due to God, and that rejecting His counsel and reproof leads to ruin.