What are the good deeds and words that make one's scales heavier on the Day of Resurrection and are likely to save him from Hell? Would you please mention the evidence?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Every good deed will make the scales heavier on the Day of Resurrection. Likewise, every bad deed will make the scales lighter on that Day. Almighty Allah says (what means): {Indeed, Allah does not do injustice, [even] as much as an atom's weight.} [Quran 4: 40]

It was narrated on the authority of Abu Hurayrah that when the Messenger of Allah, sallallaahu ‘alayhi wa sallam, was asked about donkeys and if someone good earn good deeds through them, he replied, “Nothing particular was revealed to me regarding them except the general verse where Almighty Allah says (what means): {So whoever does an atom's weight of good will see it, And whoever does an atom's weight of evil will see it.} [Quran 99: 7-8]” [Al-Bukhari]

The greatest thing to make one's scales heavier on the Day of Resurrection is doing what is beloved to Allah, which is performing religious obligations and duties. It was narrated through a qudsi hadith that Allah said, “My servant does not draw near to Me with anything more beloved to Me than that which I have made obligatory upon him…”

All other good deeds should be next to this. At the end of the above hadith, Allah said: “…My slave keeps drawing nearer to Me with voluntary deeds until I love him.”

It is mentioned in a report that a voluntary act of worship is not accepted unless the obligatory act is performed. The best voluntary act is that which is of the same kind of the obligation and is complementary of it, such as the regular voluntary prayers before and after the obligatory prayers, the voluntary fast, the voluntary charity after paying (the obligatory) zakah, the voluntary Hajj (pilgrimage) after performing the obligatory one, etc.

Having mentioned this and now that you have come to know the degrees of the acts of worship, let us mention some texts speaking about some other deeds that make one's scales of good deeds heavier on the Day of Resurrection. This is to indicate the importance of these deeds and their great virtues and to urge people to do them.

It was narrated on the authority of Abu Hurayrah that the Prophet, sallallaahu ‘alayhi wa sallam, said, “There are two words that are beloved to the Most Merciful, light on the tongue, and heavy in the Scales: Subhan Allah wa bihamdihi, (and) Subhan Allah Al-‘Atheem (Glory and praise be to Allah, glory be to Allah, the Great).” [Al-Bukhari and Muslim]

‘Abdullah ibn ‘Amr Ibn Al-‘As narrated that the Messenger of Allah, sallallaahu ‘alayhi wa sallam, said:

“Allah will select a man from my Ummah (nation) before all creatures on the Day of Resurrection, and He will display to him ninety-nine records, each of which will be as long and wide as the sight can reach. Then He will say, “Do you deny anything from this? Were My guardian scribes unjust to you?” He will say, “No, O my Lord.” Allah will say, “Do you have any excuse?” He will say, “No, O my Lord.” Allah will say, “Yes, you do, for there is a good deed for you with Us, and on this Day you will not suffer from any injustice.” Then a card containing, “I testify that there is no god worthy of worship but Allah and that Muhammad is His servant and Messenger,” will appear. Then Allah will say, “Witness your scales.” He will say, “O my Lord, what is this card (supposed to do in comparison) with these records?” Allah will say, “No injustice will be done to you.” Then the records will be put on a scale and the card on the other scale, and the records will become light and the card heavy, as nothing is heavy (when compared) with the Name of Allah.” [At-Tirmidhi, Ahmad, Ibn Majah, Al-Hakim and Ibn Hibban]

It was narrated on the authority of Abu Salam, the slave of the Messenger of Allah, sallallaahu ‘alayhi wa sallam, that he said:

“Well done! Well done! Five things how heavy they will weigh in the scale: La ilaha illa Allah, Allahu Akbar, Subhan Allah, Al-Hamdulillah, and a righteous son who dies and his parents seek the reward of Allah ... Well done! Whoever meets Allah believing in them (the following) will enter Paradise: if he believes in Allah, the Last Day, Paradise and Hell, resurrection after death, and the Reckoning.” [Ahmad]

It was narrated on the authority of Abu Ad-Darda’ that the Prophet, sallallaahu ‘alayhi wa sallam, said, "There is nothing that has a heavier weight in the scales of the believer on the Day of Judgment than good morals." [Abu Dawood, At-Tirmithi and others]

It was narrated that the Messenger of Allah, sallallaahu ‘alayhi wa sallam, met Abu Tharr and said to him, "O Abu Tharr, shall I not point out to you two traits of character that are very light on the back but very heavy on the scale?" He said, "Yes, O Messenger of Allah." He said, "Observe good morals and long silence. By Him in whose hand my life is, mankind can do nothing that compares to them." [Abu Ya‘la]

It was narrated on the authority of Ubayy that the Prophet, sallallaahu ‘alayhi wa sallam, said:

Whoever attends the funeral until the prayer is offered and it (the body) is buried will have two qirat (of rewards). Whoever attends the funeral until the prayer is offered will have one qirat (of reward). By the One Who has the soul of Muhammad in His hands, a single qirat is heavier than Mount ‘Uhud. [Ahmad]

Allah knows best.