1 Kings 11:9
And the Lord was angry with Solomon, because his heart was turned from the Lord God of Israel, which had appeared unto him twice,
Cross-reference
In 1 Kings 11:2, the Lord warned that foreign wives would turn hearts away — this is the very command Solomon broke, leading to God's anger.
In 1 Kings 11:3, Solomon's wives turned his heart — this verse explains exactly what made God angry in the main verse.
1 Kings 11:33 explains Solomon's sin: he worshiped other gods and didn't follow God — the reason for God's anger here.
1 Kings 3:5 records the first time God appeared to Solomon at Gibeon — referenced here as one of the two appearances.
1 Kings 9:2 records the second time God appeared to Solomon — directly referenced here as the appearance that came with warning.
In Deuteronomy 7:4, God warns that intermarriage will turn hearts away and kindle His anger — exactly what happened to Solomon here.
In Psalm 78:58-60, Israel provoked God with high places, exactly what Solomon did — His anger and rejection directly echo that pattern.
Hosea 4:11 says whoredom takes away the heart — Solomon's many foreign wives led his heart astray.
2 Timothy 4:10 tells of Demas deserting Paul for love of the world — just as Solomon deserted God for worldly loves.
1 Chronicles 28:7 records God's conditional promise to establish Solomon's kingdom if he obeyed — Solomon's heart turning away broke that condition.
Proverbs 4:23 commands guarding the heart with all vigilance — Solomon failed to guard his heart, which turned away.
Isaiah 29:13 describes people whose hearts are far from God despite lip service — Solomon's heart similarly turned away.
In Deuteronomy 9:8, God's anger burned against Israel at Horeb for idolatry — here too, His anger kindles against Solomon for turning away.