What is the ruling on one who wishes to marry a second wife while he forsakes his first wife for the most trivial reasons, and justifies his abandonment by claiming that any mistake on her part falls under the obedience due to the husband, even though she strives to please him?

It is permissible for a man to marry a second wife. It is not permissible for a husband to abandon his wife without a legitimate Shar'i reason, or to abstain from her if it harms her right to conjugal relations. The husband must care for his wife, fulfill her rights, and consider her feelings. The wife must be patient, adorn herself for her husband, be gentle with him, and advise him with wisdom and good counsel.