Hadith: I have not been ordered to build lofty mosques

عن ابن عباس رضي الله عنهما ، قال: قال رسول الله صلى الله عليه وسلم : «ما أُمِرْتُ بِتَشْيِيد المساجد»، قال ابن عباس: لتُزَخْرِفُنَّها كما زَخْرَفَت اليهود والنصارى.
[صحيح] - [رواه أبو داود]

Ibn ‘Abbās (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "I have not been ordered to build lofty mosques." Ibn ‘Abbās added: "You will surely adorn them as the Jews and Christians did (with their synagogues and churches)."
Sahih/Authentic. - [Abu Dawood]

Explanation

The meaning of the 'Tashyeed' of the mosques here is building high and lofty mosques, as Al-Baghawi said. However, there is nothing wrong with building and strengthening the mosque and perfecting its construction in a professional way, yet without decoration, embellishment, and adornment; so long as it does not involve ostentation, showing off and seeking fame. This is supported by the Hadīth of ‘Uthmān ibn ‘Affān: "Whoever builds a mosque for the sake of Allah, Allah builds for him the like of it in Paradise." The mosque of the Prophet (may Allah's peace and blessings be upon him) was made from adobe, its roof from palm branches, and its pillars from palm timber. Abu Bakr (may Allah be pleased with him) did not add anything to it. When the wood and palm branches began to rot during the caliphate of ‘Umar ibn al-Khattāb (may Allah be pleased with him) he restored it to its original construction and added to it. During the caliphate of ‘Uthmān (may Allah be pleased with him) he added a lot to it, building its walls from stones and plaster, and making its pillars from stones and its roof from oak, thus adding to it what would strengthen it, not adorn it. All what he did was for stabilization and plastering, without embellishment and adornment. As for the engraved stones, they were not engraved by his command; rather, they simply happened to be engraved. Those who were not pleased with his act from among the Companions had no evidence supporting its (engraved stone) prohibition except the encouragement to follow the example of the Prophet (may Allah's peace and blessings be upon him) as well as that of ‘Umar, in the construction of the mosque while avoiding luxuries. Yet, it does not entail prohibition or dislike of strengthening mosques.