What is the clearest difference in source between iqtibās and taḍmīn?

Iqtibās and Taḍmīn: Quoting Scripture and Incorporating Poetry

• Iqtibās uses Qur’an/Hadith; taḍmīn uses another poet’s verse
• Iqtibās uses another poet; taḍmīn uses Hadith
• Both use only a poet’s own earlier verse
• Both always use popular proverbs alone