What are the signs of Allah's pleasure with His servant, and is he who lives without tribulation and fulfills his religious obligations as he should considered happy in both worlds, and must every tribulation necessarily be due to a sin?

Worship and piety are the foundation of happiness, while disobedience is a harbinger of ill fortune and can be a cause for punishment in this world and the hereafter. One can refer to Ibn al-Qayyim’s book "Al-Jawab al-Kafi" in this regard. The sign of Allah's pleasure with a servant is steadfastness in obedience and excelling in good deeds, as stated in His saying, the Most High: "And those who followed them in goodness – Allah is pleased with them and they are pleased with Him." And in the Qudsi Hadith: "My servant continues to draw near to Me with supererogatory deeds until I love him." Steadfastness brings happiness in this world and the hereafter, but it does not prevent trials, which may be for expiation of sins, elevation of ranks, purification of faith, or a punishment for disobedience. Trials are not limited to calamities but also include good fortune and ease, as stated in His saying, the Most High: "And We test you with evil and with good as a trial; and to Us you will be returned."