Is it considered a lie for me to tell someone who wants to borrow money from me, "I don't have any," even though I have savings for future purposes? And are there specific conditions that must be met by the person who wants to borrow from me, such as being someone who performs prayers?

A goodly loan (qard hasan) is an act of charity and a means of drawing closer to Allah. It is better for one who has surplus wealth beyond their needs to lend it to those who ask, seeking reward and showing compassion to the needy.

However, one must refrain from lending if it is known or highly probable that the money will be used for disobedience. This ruling applies to both disobedient Muslims and non-Muslims, based on the words of Allah Almighty: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." (Al-Ma'idah: 2).

Indeed, the Prophet, peace and blessings be upon him, engaged in buying and selling with Jews and others, and Muslims continue to deal with disobedient individuals unless it involves aiding them in their disobedience.

However, if refusing to lend deters the disobedient person from their sin, then it is obligatory to refrain from lending to them, as this helps them in righteousness and piety. This is in accordance with what Sheikh al-Islam Ibn Taymiyyah mentioned in Majmu' al-Fatawa, that whoever is known for openly abandoning obligations or committing prohibited acts deserves to be boycotted (hajr) as a reprimand until they repent. He also stated that boycotting is permissible if its benefit outweighs its harm, such that it leads to weakening evil; otherwise, it is not.