What is the ruling on a husband delaying prayer until its very last moments, even minutes before the adhan of the next prayer, when he is not busy?

It is not permissible to delay prayer beyond its prescribed time without a legitimate Shar'i (Islamic legal) excuse. Whoever delays it commits a grave sin and becomes subject to the warning in the Almighty's saying: "So woe to those who pray [But] who are heedless of their prayer" (Al-Ma'un: 4-5). The husband must repent and be diligent in performing the prayer on time and in congregation, according to the Prophet's (peace be upon him) saying: "Prayer is at its appointed time." The wife should advise him with wisdom and good counsel, without quarreling.