The transition of leadership from Moses to Joshua brings massive challenges, both on the military front against the Canaanite nations and internally managing the Israelites. To ease these fears, God grants the new leader a multi-dimensional guarantee of absolute backing, ensuring his success and authority across all areas.
God begins by assuring Joshua that no person will be able to stand against him, rise up, or overcome him [מצודת דוד, ביאור שטיינזלץ]. Commentators offer different perspectives on who might attempt to challenge him. One approach views this as a military guarantee directed outward: Joshua will be an undefeated commander, and no nation will be able to withstand his forces. However, this absolute military dominance is promised exclusively for his own lifetime, standing in contrast to the later era of the Judges when the Israelites would sometimes suffer defeats and flee from their enemies [ביאור שטיינזלץ, אברבנאל]. The primary approach among commentators, however, interprets this guarantee internally. God promises that no one from within the Israelites will rise up to question his leadership, speak out against him, or demand shared power. Through this, Joshua is assured he will be spared from the kinds of internal rebellions that plagued Moses, such as the uprising of Korah and his followers [מלבי״ם, אלשיך, אברבנאל].
The assurance continues by drawing a direct comparison to the previous leader. God promises to rest His divine presence upon Joshua and assist him, just as He helped Moses stand against Pharaoh [מלבי״ם, צאינה וראינה, אלשיך]. Since the successful conquest of the land depends entirely on God's salvation, it is fitting that Joshua receives the exact same guarantees as his teacher [אברבנאל]. Although Moses experienced open, supernatural miracles while Joshua's victories will largely unfold through natural means, God promises that His divine providence will accompany the new leader with the exact same intensity [ביאור שטיינזלץ].
Finally, God promises never to loosen His grip on Joshua, ensuring he will not experience weakness, and vows never to abandon him [מצודת דוד, ביאור שטיינזלץ]. Commentators view these two assurances as a dual, complementary promise. Some explain this as a blend of physical and spiritual support: God will continually hold Joshua's hand to provide constant physical strength, while simultaneously never leaving him, ensuring the Holy Spirit remains with him [מלבי״ם]. Another approach takes this promise to a deeper spiritual level, suggesting that God will actively protect Joshua from negative forces and sin. While even Moses stumbled at the Waters of Meribah, God guarantees that He will personally prevent Joshua from falling into spiritual weakness, meaning He will never have to abandon him as a punishment for wrongdoing [חומת אנך, אלשיך]. Finally, some extend this ultimate protection even beyond death, explaining that God promises never to abandon Joshua's physical body, protecting it from decay in the grave [אלשיך].