Numbers 16:5–6, Who is his…take censers. Incense is a biblical metaphor for the prayers of men coming up before YHVH’s throne (Rev 5:8; 8:3). YHVH accepts some men’s prayers as holy and rejects the prayers of other men whom he deems not to be holy.
The story of Korah teaches us that YHVH doesn’t hear the prayers of self-centered, self-seeking, prideful and jealous rebels such as Korah et al (Prov 15:29). YHVH’s ears are open to the prayers of the righteous (Ps 34:15; 1 Pet 3:12; Jas 5:16; Heb 11:6).
The prayers of a righteous man can be hindered, as well, due to unrighteous behavior such as not treating his wife in a godly manner (1 Pet 3:7) or because we have ought with our brother (Matt 5:23–24).